The philosopher and commentator Shankara (8th century) composed commentaries to eleven Upanishads. These mukhya Upanishads are generally regarded as the oldest ones, spanning the late Vedic and the Mauryan periods. By the 17th century, there was a large number of Upanishads: The Muktika Upanishad (predates 1656) lists 108 Upanishads. The number