The Maandookya Upanishad is a part ofAtharva Veda.It is one of the shortest Upanishadsand containins only 12 verses. However,its has no bearing with the knowledge it containes . In fact, the Muktikopanishad says that if a person cannot afford to study all of the Upanishads,reading the Maandookya Upanishad suffies all.

This Upanishad refers to four states of consciousness - wakefulness, dreaming, dreamless sleep and the Absolute or Self, explained through the principle of AUM. AUM consists of three elements - a, u and m. The a refers to the state of wakefulness (jagrata), in which one is aware of sensory experiences. The u refers to the state of dreaming sleep (svapna), where only the mind is awake. The m refers to the state of dreamless sleep (susupti) in which only the Atman is aware of this experience.The Fourth state turiya that is the scilence that follows the chant of AUM.

Turiya literally means The Fourth is the ultimate state of consciousness and transcends all the three preeciding levels. It is consciousness itself.