The Yoga Sutras by Patanjali

Dating from about 150 B.C., the work shows dualist and Buddhist influences. In the Yoga tradition, Patañjali is a revered name. This Patañjali's oeuvre comprises the sutras about Yoga (Yogasūtra) and the commentary integral to the sutras, called the Bhāṣya. The Yoga Sūtras of Patañjali are 196 Indian sutras (aphorisms) on Yoga. The text fell into obscurity for nearly 700 years from the 12th to 19th century, and made a comeback in late 19th century due to the efforts of Swami Vivekananda and others. It gained prominence again as a comeback classic in the 20th century.

Must read if you are interested in Yoga or meditation.