Three works in one pair of covers. The Sutras are a set of mental pegs on which to hang the principles and precepts of a system which you must learn from a living teacher of your 'school'.
The Bhasya of Vyasa is a reinvestiture of the skeleton of the Sutras with the flesh and blood of comprehensible details. And the Tika of Vacaspati is of course a commentary on the Bhasya. The Bhasya is the oldest written systematic exposition of Yoga-doctrine in Sanskrit that we possess.
Of the Hindu philosophies, by far the most important are the ancient dualism called Sankhya, the monism of the Vedanta and the Yoga-system. Kautilya, Prime Minister of Candragupta (300 B.C.), mentions Sankhya and Yoga as current in his day. But the elements of Yoga, rigorous austerities and control of the senses, are indefinitely antique, and are one of the oldest and most striking products of the Hindu mind and character.
When one considers the floods of pseudoscientific writing with which the propagandists of Indian 'isms' have deluged people, one is better prepared to appreciate the self-restraint of Dr. Woods in keeping all that pertains to miracle mongering and sensationalism in the background, and in devoting himself to the exposition of the spiritual and intellectual aspects of Yoga. His work continues the tradition of austere scholarship which has from the beginning characterized the Harvard Oriental Series.