Composed from 900 to 300 BC, the final addition to the वेदाः Vedas, उपनिषद् The Upanishads express the revelation of Ātman, the self, and Brahman, ultimate reality.

The Sanksrit word उपनिषद्, “Upanishad”, means उप- (upa-, “near to, towards”) +‎ नि (ni, “down”) +‎ सद् (sad, “to sit”) — to sit down, to meditate, to move towards, to access higher dimensions, to receive a revelation, a teaching, a lesson. Put simply, Upanishads **are lessons. But not just any kind of lesson, spiritual lessons. These are esoteric, secret doctrines, with mystical meanings, words of mystery. They contain “true knowledge and instruction regarding the supreme spirit.”