Yoga Sutra 3.39 mastering the upgoing vital current udana
Sūtra III.39
By mastering the upgoing vital current (udāna), he passes untouched over water, mud, thorns and so on, and at death he takes the upward course
Life is the operation of the totality of the senses, as prāṇa, etc. Its activity is five-fold. Prāṇa has its operation passing through the nostrils of the face as far as the heart; the samāna life-current, so-called because it evenly (sama) guides (āna), i.e. functions, as far as the navel; apāna is so-called because it guides (āna) down (apa), operating down to the soles of the feet; udāna leads upward (ūrdhvam), having its operation from the soles to the top of the head; pervading all is the vyāna life-current. Of them, prāṇa is the principal one.
By mastering the udāna, he passes untouched over water and thorns and so on. Having mastered it, at death he takes the upward course.
By mastering the upgoing vital current (udāna), he passes untouched over water, mud, thorns and so on, and at death he takes the upward course. Life is the operation of the totality of the senses, as prāṇa, etc.; living is the operation of all eleven senses. As a dovecot moves with the movement of the birds in it, so by the unitedly reinforced operation of all the senses without exception, the body is sustained; and that is its life. Of that life, controlled by the obligation to fulfil the purposes of Puruṣa, the activity is five-fold, differentiated into prāṇa (forward-going current), apāna (downward-going), vyāna (pervading), udāna (upward) and samāna (equalizing), pervading all is the vyāna (vi-variously) life-current.
Of them prāṇa has its operation passing through the nostrils of the face as far as the heart. The samāna life-current, so-called because it evenly (sama) guides (āna), has its operation as far as the navel: it functions as far as the navel region. Apāna is so-called because it guides (āna) down (apa) the urine and faeces, etc., and from the navel operates down to the soles of the feet. Udāna is so-called because it leads upward (urdhvam) in the body, having its operation from the soles to the top of the head.
Of them, prāṇa is the principal one. From mastering that, there follows mastery of apāna and the others. A method of mastering them is given in detail in Hairanyagarbha, but as their mastery follows from mastery of mind (manas), here no separate method is given. But from mastery of prāṇāyama they are also conquered. Here without concerning himself with describing particular methods of mastering them separately, he simply gives the result of conquering udāna. He passes untouched over water, mud, thorns and so on; the and so on extends it to e.g. a sword’s edge, at death he takes the upward course, which will come about spontaneously.