Chandogya Upanishad
Also known as: Chāndogya Upaniṣad
Meditation, sound (Om/Udgitha), Brahman, Atman, and unity of existence
The Chandogya Upanishad is one of the oldest, longest, and most revered Upanishads. Its rich tapestry of dialogues, parables, and profound philosophical declarations, especially 'Tat Tvam Asi,' has made it a cornerstone of Vedantic thought and a timeless source of spiritual wisdom.
Key Idea: Tat Tvam Asi - Thou art That; the non-dual identity of Atman and Brahman.