The Yoga Sutras of Patanjali The Book of the Spiritual Man

Patanjali, also called Gonardiya, or Gonikaputra, (flourished 2nd century BCE or 5th century CE), author or one of the authors of two great Hindu classics: the first, Yoga-sutras, a categorization of Yogic thought arranged in four volumes with the titles "Psychic Power," "Practice of Yoga," "Samadhi" (state of profound contemplation of the Absolute), and "Kaivalya" (separateness); and the second, the Mahabhashya ("Great Commentary"), which is both a defense of the grammarian Panini against his chief critic and detractor Katyayana and a refutation of some of Panini's aphorisms.

The Yoga-sutras seem to span several centuries, the first three volumes apparently having been written in the 2nd century BCE and the last book in the 5th century CE. Authorities therefore tend to credit more than one author writing under this name, although there is wide variance in opinion. There is a possibility that many people used this name, because it was used by the authors of a number of other works on such diverse subjects as medicine, metrics, music, and alchemy. (britannica.com)