The Upaniṣads — the philosophical core of the Vedic tradition, revealing the nature of Brahman, the Ātman, knowledge, action and liberation. The ten principal Upaniṣads together with select minor Vaiṣṇava Upaniṣads.
A conversation between Śaunaka and Pippalāda on the four abodes within a person: where the spirit dwells in waking, in dreaming, in deep sleep, and in the fourth state. The text has come down poorly, and we do not smooth over its obscure places, but note them honestly.