that the Svesvatara-upanishad, or the Svetâsvatarânâm Mantropanishad, though bearing many notes of later periods of thought, is quoted by Saṅkara in his commentary on the Vedânta-sûtras; while the Nrisimhottaratâpanîya-upanishad forms part of the twelve Upanishads explained by Vidyâranya in his Sarvopanishad-arthânubhûti-prakâsa. The Upanishads comprehended in that work are:
11. Talavakâra (Kena)-upanishad.
The number of Upanishads translated by Dârâ Shukoh amounts to 50; their number, as given in the Mahâvâkyamuktâvalî and in the Muktikâ-upanishad, is 108. Professor Weber thinks that their number, so far as we know at present, may be reckoned at 235. In order, however, to arrive at so high a number, every title of an Upanishad would have to be counted separately, while in several cases it is clearly the same Upanishad which is quoted under different names. In an alphabetical list which I published in 1865 (Zeitschrift der Deutschen Morgenländischen Gesellschaft XIX, 137-158), the number of real Upanishads reached 149. To that number Dr. Burnell  in his Catalogue
- Vedânta-sûtras I. 1, 11.
- One misses the Îsâ or Îsâvâsya-upanishad in this list. The Upanishads chiefly studied in Bengal are the Brihad-âranyaka, Aitareya, Khândogya, Taittirîya, Îsâ, Kena, Katha, Pnasma, Mundaka, and Mândûkya, to which should be added the Svetâsvatara. M. M., History of Ancient Sanskrit Literature, p. 325.
- Dr. Burnell thinks that this is an artificial computation, 108 being a sacred number in Southern India. See Kielhorn in Gough's Papers on Ancient Sanskrit Literature, p. 193.
- Weber, History of Sanskrit Literature, p. 155 note.
- Indian Antiquary, II, 267.