Mahabharata 6.26.29

अपाने जुह्वति प्राणं प्राणेऽपानं तथापरेप्राणापानगती रुद्ध्वा प्राणायामपरायणाः

apāne juhvati prāṇaṃ prāṇe'pānaṃ tathāpareprāṇāpānagatī ruddhvā prāṇāyāmaparāyaṇāḥ

Our plain-language meaning of this verse is waiting for scholar review.