In the yearly book of the german/austrian alpine clubs for 2010 there is an interesting article by Heinz Jungmaier: he has found some - more than 150 years old - letters that include a report about the really frist ascent: That has been done on August 30th 1855, by Josef Moritz from Eisentratten with local guides Andreas Pucher and Jakob Haman.
Interesting news! I will immediately have a look - I hope that's on the web, I usually find them.
Thanks a lot!
Aha. It's Jungmeier. There are other articles as well...