Maandukya Upanishad

The Māṇḍūkya Upaniṣad is the shortest of all the Upanishads, and is assigned to Atharvaveda. It is in prose, consisting of twelve terse verses, and is associated with a Rig Vedic school of scholars. It discusses the syllable Om, presents the theory of four states of consciousness, asserts the existence and nature of Atman (Soul, Self). The Mandukya Upanishad is an important Upanishad in Hinduism, particularly to its Advaita Vedanta school. It tersely presents several central doctrines, namely that "the universe is Brahman," "the self (soul, atman) exists and is Brahman," and "the four states of consciousness".