apane juhvati pranam
prane panam tathapare
pranan pranesu juhvati
(Bhagavad Gita, Text 29, Ch 4, Transcendental Knowledge)
Meaning: Still others, who are inclined to the process of breath restraint to remain in trance, practice by offering the movement of the outgoing breath into the incoming, and the incoming breath into the outgoing, and thus at last remain in trance, stopping all breathing. Others, curtailing the eating process, offer the outgoing breath into itself as a sacrifice.