There are four stages of Yoga evolution, until we came to practice it nowadays. The stages are Pre-classical Yoga, Classical Yoga, Post-classical Yoga, and Modern Yoga.
Pre-classical Yoga
The Upanishad (Gnostic texts) appeared between 1800-1500 B.C. It contains 200 scriptures, which explained the transcendental self, (atman) and its relationship with the reality (Brahman). Karma principles originated with the Upanishads.
Vyasa was a great sage in 1400 B.C, he had categorized the Vedic hymns into four texts we use nowadays, and they are:
