There are ten "principal" ones including the Kena, Prashna, and Isha as designated by the 8th-century mystic, Shankara.  Etymologically their name suggests "sitting down near" perhaps referring to the
There are ten "principal" ones including the Kena, Prashna, and Isha as designated by the 8th-century mystic, Shankara.  Etymologically their name suggests "sitting down near" perhaps referring to the "forest academies," out of whose teachings they arose.  Perhaps their most famous portion is the story "What the Thunder Said," which is cited in The Wasteland.  FTP, name these ancient religious texts, the so-called commentaries on the Hindu Vedas.
There are ten "principal" ones including the Kena, Prashna, and Isha as designated by the 8th-century mystic, Shankara.  
Upanishads