To those who love the truth. "The Upanishads are ancient treatises, written in Sanskrit, containing the theosophy of the Vedas. They are often referred to as rahasya, the 'mystery' or 'secret, ' as being formerly taught only to those who had gone through a special preliminary training and given proof of their fitness; they are also called shruti-shirah, or the 'head of revelation, ' as being the most precious revelation handed down to the Aryan inhabitants of India.