Yoga developed in the Indus-Sarasvati civilization in Northern India, some five thousand years ago. The first mention of the word yoga was in the Rig Veda amongst the songs and mantras that were used by the Vedic priests. Yoga was slowly developed and defined by the Brahmans and Rishis who documented their practices and beliefs in the Upanishads. The most renowned Yogic scripture is the Bhagavad-Gîtâ, composed around 300 B.C.E. As a result of internalizing the Vedas' idea of ritual sacrifice, the Upanishads advocated the sacrifice of the ego through self-knowledge, action, and wisdom.
Rig Veda - an ancient collection of sacred texts.
Brahmans and Rishis - Hindu spiritualists.
Upanishads - Sacred scriptures.
Bhagavad-Gîtâ - Song of God, a 700 verse poem and the most important religious text of Hinduism.