The AUM Mantra

The most important mantra in yoga is the mantra AUM.
AUM is the sound with which existence began, continues on its journey, and will eventually end. This mantra encompasses the trigunas as well as the states of waking consciousness, the dream state, and deep sleep. If you listen carefully, you may even experience the fourth state of consciousness, Turya Avasta, where you become completely thoughtless: AUM.