In the Brihadaranyaka Upanishad, King Janaka offers a thousand cows as a prize for the most learned scholar. Yajnavalkya claims them, and the other scholars challenge him one by one. One of them is a woman, Gargi Vachaknavi. She asks him a series of questions.
At last he stops her: “Do not, O Gargi, push your inquiry too far, lest your head should fall off.”