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 survey of the whole of yoga in four kinds — mantra, laya, haṭha, and rāja — with a description of the stages, hindrances, and signs of success. It ends with the word "service": the practice is named not work for oneself, but service.