Yoga Sutras of Patanjali

About two millennia ago, the sage Patanjali synthesized and organized the teachings on yoga from older traditions into an intricately connected sequence of aphorisms. Hindu tradition regards The Yoga Sutras of Patanjali as the foundational text of yoga philosophy. The work fell into obscurity from the 12th to the 19th century, returning to prominence only in the late 19th century due to the efforts of the Theosophical Society and then Swami Vivekananda and others.
This edition, translated by the Sanskrit scholar and Theosophist Charles Johnston, contains the sutras and a commentary, and is a simple introduction in English to yoga philosophy.