Asana is the third rung in the ladder of the practice of yoga. If the yamas and niyamas are the foundation of yoga, asana may be regarded as its threshold. 'Asana', literally, means a seat. Here 'seat' does not mean a cushion or some such thing that is spread on the ground. Asana is a pose of the body or the posture which it assumes at the commencement of the practice. It is called a 'seat', because it is a posture of sitting and not standing. While there exist many asanas, such as the 'sirsha', etc., there is only one set of postures which can be taken as aids in meditation. A sitting posture is asana, because to stand and meditate may lead to a falling down of the body, and lying down may induce sleep. The sitting posture is therefore the most conducive to concentration of mind. That there are many other asanas like sirsha, sarvanga, etc., need not deter us from a choice of the asana for meditation. The Hatha Yoga prescribes several postures for different purposes. These asanas of the Hatha Yoga are coupled with certain other practices, called bandhas, mudras and kiryas, in addition to pranayama. While asana is a pose, bandha is a lock of the limbs of the body intended to direct the prana in a particular channel and centring it in a given location. Mudra is a symbol. It also means a seal or fixing up of the limbs. The two types of mudras are those which seal up the prana and which symbolise meaning by a gesture. Kriya is a process of purification, so that the body may be fit for asana and the others. The purpose is to make the body healthy and free from inertia as much as possible. Neti or cleansing the nostrils, basti or washing the colon, dhauti or cleaning the stomach, nauli or churning the abdomen, trataka or gazing for training the eyes by concentration, and kapalabhati or chastening the brain and the skull are the main kiryas in Hatha Yoga. The physical body is characterised by dullness, torpidity, etc., which bring about sluggishness and sleep, in which condition meditation cannot supervene. The bandhas etc. free the body from tamas, make it flexible, easily adjustable and healthy. This is the general effect produced by asanas, bandhas and mudras. All these are the preliminary exercises, and Hatha Yoga is a preparation for Raja Yoga. While there are many asanas in Hatha Yoga, there are only a few in Raja Yoga, and finally we come to a single asana. This final asana is called dhyana-asana or the meditative pose. 

How does asana help one in meditation? The relation between the individual and the universal has to be brought to mind in this connection. There is an organic tie between the individual and its environment, and the purpose of yoga is to rouse to consciousness this inherent harmony. This is to be brought about in successive stages. Whatever one is, and whatever one has, should be set in tune with the universal. This is yoga, ultimately. When the personal individuality is attuned to universal being, it is the condition of yoga. The individual begins with the body, but there are many things within the body, as there are in the physical cosmos. There are prana, senses, mind, intellect, etc., encased in the body. All these things within have to be in gradual union with the universal. The mind cannot be so attuned when the body is in revolt. Yoga requires union of everything in the personality with the universal. Asana is the initial step in yoga, whereby the bodily structure is set in unison with the cosmos. When an individual thinks in terms of the ego, which is self-affirmation, with a selfish attitude towards the things of the world, there is internal disharmony. The more is one unselfish, the more also is one concordant with reality, and the more is the selfishness, the more also is the discordant note struck in one's life. yoga is a systematized process of establishing permanent friendship with Nature in all its levels - friendship in the physical, vital, mental, intellectual and spiritual levels. It is all love and friendship, and no enmity anywhere. This is yoga. The yoga system is an exact science which takes into consideration every aspect of life, in a slow process of unfoldment. The lowest manifestation is the physical or the bodily personality. 

The asana should be firm and easy. It should be steady and not cause discomfort of any kind. It should not make the student conscious of the body through tightness, tension, etc. It should be a normal posture in which he can sit for a long time. The yoga prescribes certain minimum requirements in asana, though a long rope is given when it is merely said that it is the firm and comfortable. Within the limits of the rule, one may have freedom in asana. What are the limits? The extremities of the body should be locked, and the head, neck and spine should be in a straight line. These extremities are the fingers and the toes. If they are left exposed, the electric current generated in meditation may leak into space. Also, one should not sit on the bare ground, because the earth is a conductor of electricity and the energy may thereby leak again. A non-conductor of electricity is prescribed as good material to spread on the ground. In olden days a dry grass mat was used, called the kusa asana over which a deer-skin, and a cloth, both non-conductors of electricity, were spread. The Gita prescribes that the seat should not be too high or too low. The student may fall down if the seat is very high, and if it is too low, there is the likelihood of insects and reptiles creeping into the seat. The spine, too, should be kept straight. It should be at right angles to the base. One should not be leaning against any support or be bending forward. The reason is that if the spine is straight the nerves get relaxed and no part of the body exerts influence on another part. The flow of the prana through the nerves is smoothened. If the body is twisted, the prana has to make effort to flow through the limbs. There is a free movement of energy in the body when the whole system is in a state of relaxation. 

Apart from the spine being straight, and the extremities being locked, the legs are to be bent in three or four ways. There are padma-asana, siddha-asana, svastika-asana and sukha-asana. One can choose any of these postures for meditation. The purpose of a fixed asana is to enable the mind to slowly forget that there is a body at all. The body will attract attention, somehow. But the mind cannot, in meditation, afford to remain conscious of the body. The student gradually loses sensation of the limbs. He forgets that he is seated, that he has a body or the limbs. The first sign of successful practice in asana is a sense of levitation. The body is felt to be so light that it may appear to be ready for a rise. This sensation comes when there is a thorough fixity of posture. This is the test. One will begin to feel a creeping sensation as if ants are crawling over the body. That should show the student's readiness for a rise above body-consciousness. Together with these sensations, he will also realize a kind of satisfaction, a happiness, a delight that comes due to lightness of the body in asana. If one sits thus for two to three hours, one may not have any feeling even if someone touches the body. The prana is so harmonious that it does not create sensation in the body. It is disharmony that creates sensations of things. When the highest harmony is reached, there will be no external sensation. With extremities locked; with fingers kept one over the other, or locked; with spine straight; head, neck and spine in one line, and at right angles to the base of the body; the asana is perfect. 

The asana should be effortless. There should be no effort not only in the body but also in the mind. Absolute ease of relaxation is the sign of perfected asana. The student should be in a most natural condition in which he is not conscious even of his breathing. If there is pain, jerk, or a pinching sensation, it should mean that the asana is not properly fixed. There is a prescription given by Patanjali to quicken fixity of posture. And that is 'attention on the infinite'. Steadiness is nowhere to be found in the world. There is only oscillation and fleeting of things everywhere. Fixity is unknown, as it is all motion in the world. There is only one thing that is fixed, viz., the infinite. All finites move and change. If the student can concentrate his mind on the infinite, he would imbibe certain qualities from it, the first being fixity. 

Here concentration is to think nothing in particular but all things at once. Though no one can think of the infinite as it is, one can think everything in the sense of inclusion of everything that comes to the mind. This is the psychological infinite. The imagined infinite created in the mind helps the student in fixing himself in an asana and in stabilizing his emotions. Contemplation on the infinite is thus a means to perfection in asana. 

When this bodily control is achieved, there comes freedom from the onslaught of what are called the 'pairs of opposites', such as heat and cold, hunger and thirst, joy and grief, and so on. Anything that creates a tension in one's system is a pair of opposites. These are overcome by a perfected practice of asana. The pairs of opposites become active in our system when the prana becomes restless. The restlessness of the prana causes hunger and thirst. When the prana is poised, there is a lessening of the feeling of the pairs of opposites. The prana is calmed not only by the practice of pranayama but also by asana. When the body remains in a state of balance, the prana too tends to be harmonious, even as the mind becomes tranquil when the sensations are harmonized. Distracted sensations disharmonize the thoughts. What the senses are to the mind, the body is to the prana. As harmonized sensations create a harmonious set of thoughts, the harmonized body ushers harmony of the prana. There is always a connection between the outer and the inner. 

Also, we are asked to face the East or the North in meditation, because of certain magnetic currents produced from these directions, due to sunrise and to the effect of the pole of the North. The place selected, too, should be free from distracting noise, from gnats and mosquitoes, etc., and from the chirping of birds, and the like. A temperate climate is desirable (which means to say that one cannot engage oneself in the practice when it is too hot or too cold, because of chances of increase in body-consciousness thereby). When the student is seated in asana, with a harmonious flow of the prana through the nerve-channels, he has already entered the gates of meditation. Asana has a spiritual import. One knocks at the door of the palace of the immortal, here. While in yama and niyama one is in preparation, in asana the gates of Reality are reached, though they are yet to be opened. The soul is there ready to meet the Sovereign of the universe. This is the first step in actual yoga. 

The yoga prescribes at least three hours of daily practice in a steady posture, when one is supposed to have mastered asana (asana-jaya). The body is the vehicle of the nerves, the nerves are the channels of the prana, the prana is an expression of the mind, and the mind it is which practices meditation, in the end. There is this long linkage, and so the moment a harmonious posture is assumed, the mind receives an intimation thereof. The body is at once calmed down in its metabolic process, and hunger and thirst are lessened. The forces of hunger and thirst are symptoms of an agitation of the prana, and when the prana is set in harmony, the agitation should come to a minimum. Hence, the student's hunger and thirst are reduced to the least. The cells of the body find more time to construct themselves rather than deplete energy and make progress through mellowed emotion. Even emotions can be subdued by asana, for here one inhales and exhales calmly, and so the cellulary activity of the body comes down, the nerve-channels are opened up for a rhythmic flow of the prana, and a rhythm sets in everywhere. Yoga is rhythm. Asana is therefore the beginning of yoga, wherein one starts relating oneself to the cosmic order.