The four holy Vedas were composed during the Vedic period (c. 1500–500 BCE) in the northwest of the Indian subcontinent by the ancient sages who heard the eternal apauruṣeyā knowledge. They contain prayers to devās or personified forces of nature and the Ultimate Reality. They also contain yajña rituals—⁠—yajña is variously defined as a journey, climbing a hill, a battle, and also worship or rite; the ritual action is not performed by a human but by devās at the request of a human—⁠—and philosophical discourses on the nature of Paramātmā, the soul, and the world. These discourses include the Upanishads, literally “sitting down near” a teacher, vedantic knowledge appended to the end of each Veda.