The Svetasvatara Upanisad similarly says that a yogi should hold the body erect, repress the breathing and restrain the mind as he would ‘a chariot yoked with vicious horses’. This yoking of the mind leads to inner visions and, more importantly, ‘a body made in the fire of yoga’ which ensures that the wise man is healthy, freed from sorrow, his purpose completed.
Parts of the famous epic poem the Mahabharata contain passages describing the practice of yoga, such as postures, breath control, inner vision, the yoga of inner sound (nada, sabda), and descriptions of esoteric or subtle anatomy.
The most famous of the Yoga Upanisads, the Yogatattva, mentions four kinds of yoga: mantra-yoga, which involves the repetition of mantras; laya-yoga, the symbolic dissolution of the cosmos within the body and the raising of a corporeal energy known as Kundalini; hatha yoga, the yoga of ‘force’ focusing on various asanas, pranayama, visions of light, and inner sound; and raja-yoga (‘royal’, or simply ‘the best’, yoga), which is the classical system of Patanjali Yoga, which also mentions the magical powers (siddhi) gained by the yogi. Hatha-yoga itself develops an extensive literature, particularly Svatmarama’s Hathayoga-pradipika, which has links with Indian alchemy, Tantra and the Siddha tradition.