Yajnavalkya or Yagyavalkya (Sanskrit: याज्ञवल्क्य, IAST:Yājñavalkya) is a Hindu Vedic sage prominently mentioned in the Brihadaranyaka Upanishad (c. 700 BCE) and Tattiriya Upanishad. Yajnavalkya proposes and debates metaphysical questions about the nature of existence, consciousness and impermanence, and expounds the epistemic doctrine of neti neti ("not this, not this") to discover the universal Self and Ātman. Texts attributed to him include the Yajnavalkya Smriti, Yoga Yajnavalkya and some texts of the Vedanta school. He is also mentioned in the Mahabharata as well as various Puranas, Brahmanas and Aranyakas. Source: Wikipedia (en)