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 Śaiva book: the gods ask Rudra who He is, and He answers in the first person — "I alone was and am," listing all that He has become. It ends with a vow taken with ash, and instruction on to whom this teaching may be passed.