Patanjali was an Indian teacher traditionally thought of as the person who gathered and systematized the teachings of meditation and yoga. He is believed to have lived between 200B.C.E. and 450 C.E. However, he is credited with composing the small Sanskrit volume of Yoga Sutras from which the modern practice of yoga is derived.
The Sutras laid out a system of practice by which one can attain a pure state free of illusion. The practice begins with the adoption of a fivefold ethic (call yama), very similar to that taught by Mahavida and the Jains—nonviolence, truthfulness, non-stealing, sexual restraint, and non-attachment. It is followed by the adoption of five virtues (niyama)—purity, contentment, austerity, study, and dedication. These practices inhibit the negative influences of being in the world. After adopting a lifestyle centered on yama and niyama, one begins the step-by-step adoption of the asanas (postures), breath control, control over the sense, concentration, and meditation, each of which should lead to the goal of samadhi (variously described as absorption or liberation).
According to Patanjali, the practice of yoga has a number of side effects. For example, the practice of nonviolence will lead to the cessation of violence in one's presence. Some of these side effects involve distinctly paranormal activity. For example, truthfulness in one's life leads to the ability to speak the future. The practice of concentration and meditation grants a number of siddhas, unusual powers, such as the ability to remain hidden or to greatly increase one's strength. It also leads to an understanding of the subtle anatomy of the body, including an awareness of the mysterious psychic/spiritual centers generally referred to as chakras. The practice of yoga then leads to the valuing of the siddhas and those who practice them throughout Indian society.
The practice of yoga (especially that part of Patanjali's system that included the asanas,) reached a low point in the nineteenth century, but was reborn early in the twentieth century. Simultaneously, hatha yoga, that aspect of the teachings devoted to the postures, was exported to the West as a discipline centered upon the improvement of bodily health. Hatha yoga has actually enjoyed a greater response in non-Indian cultures than in the land of its birth.
Sources:
Majumdar, Sachindra Kumar. Introduction to Yoga Principles and Practice. Secaucus, N.J.: Citadel Press, 1976.
Patanjali. The Yoga Sutras of Patanjali: A New Translation and Commentary. Edited by Georg Feuerstein. Folkstoone, UK: Dawson, 1979.