"OM, this imperishable letter is all this. An exposition of this: All that existed, exists and will exist, is verily OM. And what-ever transcends the three periods of time is also verily OM. Indeed, all this is Brahman (The Omnipresent, Omnipotent, Omniscient Supreme). This Self is Brahman. The Self, such as It is, is possessed of four quarters."
(Mandukya Upanishad, Verse 1-2)

English Audio CD - 63 min.