Mbh 12.301.6a

"'Bhishma continued, "Engaged, O Bharata, in subsisting upon broken grains of rice and sodden cakes of sesame, and abstaining from oil and butter, the Yogin acquires Yoga-puissance. By subsisting for a long time on powdered barley unmixed with any liquid substance, and by confining himself to only one meal a day, the Yogin, of cleansed soul, acquires Yoga-puissance. By drinking only water mixed with milk, first only once during the day, then once during a fortnight, then once during a month, then once during three months, and then once during a whole year, the Yogin acquires Yoga-puissance. By abstaining entirely from meat, O king, the Yogin of cleansed soul acquires puissance.[1584] By subjugating lust, and wrath, and heat, and cold and rain, and fear, and grief, and the breath, and all sounds that are agreeable to men, and objects of the senses, and the uneasiness, so difficult to conquer, that is born of abstention from sexual congress, and thirst that is so terrible, O king, and the pleasures of touch, and sleep, and procrastination that is almost unconquerable, O best of kings, high-souled Yogins, divested of attachments, and possessed of great wisdom, aided by their understandings, and equipped with wealth of contemplation and study, cause the subtile soul to stand confessed in all its glory. This high (Yoga) path of learned Brahmanas is exceedingly difficult to tread. No one can walk along this path with ease. That path is like a terrible forest which abounds with innumerable snakes and crawling vermin, with (concealed) pits occurring every where, without water for slaking one's thirst, and full of thorns, and inaccessible on that account. Indeed, the path of Yoga is like a road along which no edibles occur, which runs through a desert having all its trees burnt down in a conflagration, and which has been rendered unsafe by being infested with bands of robbers. Very few young men can pass safely through it (for reaching the goal).