The main channel leading from the mouth to the anus is the path by which Yogins, knowing no fatigue, calm in happiness and misery, and highly patient, succeed in attaining to Brahma by drawing the soul within the brain.
एप मार्गोऽथ योगानां येन गच्छन्ति तत्पदम्। जितक्लमा: समा धीरा मूर्धन्यात्मानमादधन्॥