Mbh 13.142.2a

"'"'Maheswara said, "Do thou hear with concentrated attention what the duties are of forest recluses. Having listened to them with one mind, O goddess, do thou set thy heart upon righteousness. Listen then to what the acts are that should be practised by righteous recluses crowned with success, observant of rigid vows and rules, and residing in woods and forests. Performing ablutions thrice a day, worshipping the Pitris and the deities, pouring libations on the sacred fire, performing those sacrifices and rites that go by the name of Ishti-homa, picking up the grains of Nivara-paddy, eating fruit and roots, and using oil that is pressed out from Inguda and castor-seeds are their duties. Having gone through the practices of Yoga and become crowned with (ascetic) success and freed from lust and wrath, they should seat themselves in the attitude called Virasana. Indeed, they should reside in those places which are inaccessible to cowards.[566] Observant of the excellent ordinances relating to Yoga, sitting in summer in the midst of four fires on four sides with the sun overhead, duly practising what is called Manduka Yoga, and always seated in the attitude called Virasana, and lying on bare rocks or the earth, these men, with hearts set upon righteousness, must expose themselves to cold and water and fire. They subsist upon water or air or moss. They use two pieces of stones only for husking their corn. Some of them use their teeth only for such a purpose. They do not keep utensils of any kind (for storing anything for the day to come). Some of them clothe themselves with rags and barks of trees or deer-skins. Even thus do they pass their lives for the measure of time allotted to them, according to the ordinances (set forth in the scriptures). Remaining in woods and forests, they wander within woods and forests, live within them, and are always to be found within them.