1. Mandukya Upanishad - Yoga as a Science of 4 States of Human Consciousness
The Mandukya Upanishad deals with the four states of consciousness.
Waking, 2. dreaming, 3. Deep sleep and 4. Turiya or samadhi state. It also states
that everything in the universe is OM and that the past, present and future are
contained in OM. The three components or syllables comprise the three states of
Brahman. After meditation on OM one is taken to the silence which is Atman or
Brahman.