Yogatattva Upaniṣad 44

44

evaṃ māsatrayābhyāsānnāḍīśuddhistato bhavet |
yadā tu nāḍīśuddhiḥ syāttadā cihnāni bāhyataḥ ||

Then closing the right nostril with his right thumb, he should gradually draw in the air through the left nostril. Having restrained it as long as possible, be should again expel it through the right nostril slowly and not very fast. Thon filling the stomach through the right nostril, he should retain it as long as he can and then expel it through the left nostril. Drawing the air through that nostril by which he expels, he should continue this in uninterrupted succession. The time taken in making a round of the knee with the palm of the hand, neither very slowly nor very rapidly, and snapping the fingers once is called a māṭrā. Drawing the air through the left nostril for about sixteen māṭrās and having retained it (within) for about sixty-four māṭrās, one should expel it again through the right nostril for about thirty-two māṭrās. Again fill the right nostril as before (and continue the rest). Practise cessation of breath four times daily (viz.,) at sunrise, noon, sunset and midnight, till eighty (times are reached). By a continual practice for about three months, the purification of the nādis takes place. When the Midis have become purified, certain external signs appear on the body of the yogin. I shall proceed to describe them. (They are) lightness of the body, brilliancy of complexion, increase of the gastric fire, leanness of the body, and along with these, absence of restlessness in the body.