Mbh 12.307.2a

"'"Vasishtha said, 'I shall tell thee what thou askest! Listen however, to me, O monarch, as I expound to thee the practices of Yoga separately. Contemplation, which constitutes an obligatory practice with Yogins, is their highest puissance[1619]. Those conversant with Yoga say that Contemplation is of two kinds. One is the concentration of the mind, and the other is called Pranayama (regulation of breath). Pranayama is said to be endued with substance; while concentration of mind is unendued with it.[1620] Excepting the three times when a man passes urine and stools and eats, one should devote the whole of his time to contemplation. Withdrawing the senses from their objects by the aid of the mind, one possessed of intelligence, having made oneself pure, should agreeably to the two and twenty modes of transmitting the Prana breath, unite the Jiva-soul with That which transcends the four and twentieth topic (called Ignorance or Prakriti)[1621] which is regarded by the wise as dwelling in every part of the body and as transcending decay and destruction. It is by means of those two and twenty methods that the Soul may always be known, as heard by us. It is certain that this practice of Yoga is his whose mind is never affected by evil passions. It is not any other person's. Dissociated from all attachments, abstemious in diet, and subduing all the senses, one should fix one's mind on the Soul, during the first and the last part of the night, after having, O king of Mithila, suspended the functions of the senses, quieted the mind by the understanding, and assumed a posture as motionless as that of a block of stone. When men of knowledge, conversant with the rules of Yoga, become as fixed as a stake of wood, and as immovable as a mountain, then are they said to be in Yoga.