About Yajanavalkaya:

Yājñavalkya (Devanagari: याज्ञवल्क्य) of Videha (fl. c. 7th century BCE) was a sage and philosopher of Vedic India. He was one of the first philosophers in recorded history, alongside Uddalaka Aruni. In the court of King Janaka of Mithila, he was renowned for his expertise in Vedic ritual and his unrivaled talent in theological debate. He expounded a doctrine of neti neti to describe the universal Self or Ātman. He later became a wandering ascetic. His teachings are recorded in the Shatapatha Brahmana and the Brihadaranyaka Upanishad.

He is traditionally credited with the authorship of the Shatapatha Brahmana (including the Brihadaranyaka Upanishad), besides the Yoga Yajnavalkya and the Yājñavalkya Smṛti. He is also a major figure in the Upanishads.