Atharva Veda · Atharva Veda (Sāmānya-Vedānta Upanishad group) · 3 mantras
Atma Upanishad
Ātmopaniṣad
Central theme: The threefold Atman — bahyatman (gross body), antaratman (subtle/jiva) and paramatman (causal/supreme Self)
A miniature Upanishad of just three mantras attributed to the sage Angiras. Despite its brevity it lays out a complete Vedantic anthropology by distinguishing three meanings of the word "atman" — bahyatman (the outer self = the gross body with its skin, bones, marrow, nerves, hair, nails, hunger, sleep, fear, decay and death), antaratman (the inner self = the subtle body of intellect, manas, ahamkara and the ten organs, the experiencer of waking, dream and deep sleep, of the eight prakritis and the three gunas) and paramatman (the supreme Self = the pure consciousness adored with Om, beyond the three states, beyond the three bodies, beyond birth and death, the witness of all). Maps directly onto the later panchakosha-viveka and the karana-sukshma-sthula trilogy that became the staple of every Vedantic primer.
Atma Upanishad 3
अथ परमात्मा यथाक्षरमुपासनीयः । ओमित्येतस्याक्षरस्य पादाश्चतुर्थः शान्त आत्मा
Atha paramātmā yathākṣaram upāsanīyaḥ, om ity-etasyākṣarasya pādāś caturthaḥ śānta ātmā
Now the supreme Self is to be meditated upon as the imperishable — the fourth quarter of the syllable Om, the silent and peaceful Self.
Three things call themselves "I" — the body, the mind, and the silence behind both. Only the third is the Atman.