Osho calls the Sarvasar Upanishad “the secret of secrets, the mystery within all the mysteries, the essence of essences.” It is one of the most ancient texts of the rishis, the seers, of India.
In life, many things can be learned without the person undergoing any inner transformation: he can remain the same and just go on accumulating knowledge and skills. But in the realms of the inner search, unless the person is ready to change and transform through a deep and sincere inquiry, he will never understand and find the essence within.

In The Way beyond Any Way Osho describes, step by step, how to search for this essence. But he cautions, “I warn you in advance that to involve oneself in the teachings of an Upanishad is like playing with fire. An Upanishad cannot be understood without also becoming transformed.”