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The Sirr-i-Akbar (Persian: سرِ اکبر, “The Greatest Mystery” or “The Greatest Secret”) is a version of the Upanishads authored by the Mughal prince Dara Shukoh, translated from Sanskrit into Persian, c. 1657. After years of Sufi learning, Dara Shukoh sought to uncover a common mystical language between Islam and Hinduism, boldly stating that the Kitab al-Maknun, or "Hidden Book", mentioned in the Qur'an (56:78) is none other than the Upanishads.