HAṬHAYOGA is historically the most influential, and today the best known, of the several schools of yoga derived from the classical Yoga of Patañjali's Yoga Sūtra. Haṭhayoga differs from classical Yoga, and from its sister schools, principally in the special emphasis that it gives to certain aspects of yoga doctrine and practices. Classical Yoga depends heavily on Sāṃkhya metaphysics and tries to strike a balance between physical exercises and meditation. Haṭhayoga tends to prefer esoteric mysticism to systematic metaphysics and emphasizes physical exercises over meditation. It also pays particular attention to the acquisition of supernatural powers and the conquest of disease and death. The set of mystical, supraphysical concepts contained in haṭhayoga texts make it one of the principal constituents and markers of the current of Hinduism known as Tantrism.

Many of the...