अथासने दॄधे योगी वशी हित-मिताशनः |
गुरूपदिष्ह्ट-मार्गेण पराणायामान्समभ्यसेत ||

Posture becoming established, a Yogî, master of himself, eating salutary and moderate food, should practice Prâṇâyâma, as instructed by his guru.
Respiration being disturbed, the mind becomes disturbed. By restraining respiration, the Yogî gets steadiness of mind
So long as the (breathing) air stays in the body, it is called life. Death consists in the passing out of the (breathing) air. It is, therefore, necessary to restrain the breath.

The breath does not pass through the middle channel (suṣumnâ), owing to the impurities of the nâdîs. How can then success be attained, and how can there be the unmanî avasthâ. When the whole system of nâdîs which is full of impurities, is cleaned, then the Yogî becomes able to control the Prâṇa. Therefore, Prâṇâyâma should be performed daily with sâtwika buddhi (intellect free from raja and tama or activity and sloth), in order to drive out the impurities of the suṣumnâ. Sitting in the Padmâsana posture the Yogî should fill in the air through the left nostril (closing the right one); and, keeping it confined according to one’s ability, it should be expelled slowly through the sûrya (right nostril). Then, drawing in the air through the sûrya (right nostril) slowly, the belly should be filled, and after performing Kumbhaka as before, it should be expelled slowly through the chandra (left nostril).

Inhaling thus through the one, through which it was expelled, and having restrained it there, till possible, it should be exhaled through the other, slowly and not forcibly.
If the air is inhaled through the left nostril, it should be expelled again through the other, and filling it through the right nostril, confining it there, it should be expelled through the left nostril. By practicing in this way, through the right and the left nostrils alternately, the whole of the collection of the nâdîs of the yamîs (practisers) becomes clean, i.e., free from impurities, after 3 months and over. In the beginning, there is perspiration, in the middle stage there is quivering, and in the last or the 3rd stage one obtains steadiness; and then the breath should be made steady or motionless. The perspiration exuding from the exertion of practice should be rubbed into the body (and not wiped), as by so doing the body becomes strong. During the first stage of practice, the food consisting of milk and ghee is wholesome. When the practice becomes established, no such restriction is necessary. Just as lions, elephants, and tigers are controlled by and by, so the breath is controlled by slow degrees, otherwise (i.e., by being hasty or using too much force) it kills the practiser himself.

When Prâṇayama, etc., are performed properly, they eradicate all diseases; but an improper practice generates diseases. Hiccough, asthma, cough, pain in the head, the ears, and the eyes; these and other various kinds of diseases are generated by the disturbance of the breath. The air should be expelled with proper tact and should be filled in skilfully, and when it has been kept confined properly it brings success.

When the nâdîs become free from impurities, and there appear the outward signs of success, such as lean body and glowing color, then one should feel certain of success.
By removing the impurities, the air can be restrained, according to one’s wish and the appetite is increased, the divine sound is awakened, and the body becomes healthy.
If there be an excess of fat or phlegm in the body, the six kinds of kriyâs (duties) should be performed first. But others, not suffering from the excess of these, should not perform them.
The six kinds of duties are : Dhauti, Basti, Neti, Trâtaka, Nauti and Kapâla Bhâti. These are called the six actions
These six kinds of actions which cleanse the body should be kept secret. They produce extraordinary attributes and are performed with earnestness by the best of Yogîs.