Original works of great mathematicians In almost every mathematical text there is a line as This was first proved by Gauss or This formula first appeared in a work of Riemann, but for me it's more like My friend told me once that...

For my Bachelor thesis and other papers I'm working on I would prefer to add a scan of the original paper rather that a quote from a book1 that quoted book2 that found it in a book3. I was already looking for some original papers from some great mathematicians (Riemann, Euler, Cantor, Hilbert etc...) on the internet, but I got quite disappointed by results. I expected some organization that collects scans from the old scientific works and makes them publicly available, but either I was looking elsewhere or it just doesn't exist...

So my question is:
Do you know about any place (website?) where scans of original work of great old mathematicians are collected?


  Look, the scan of the first page of Riemann's original work Über die Anzahl der Primzahlen unter einer gegebenen Grösse !! Such a mathematical and historical gold...
http://archive.org

Just search for "Bernhard Riemann", for example.
This is more of a science thing, but you might be interested in De Re Metallica for its Renaissance metallurgy (no alchemy here, the thing is a prelude to modern chemistry and geology and engineering).  Both the book itself and the translation  are amazing works of scholarship.  And the woodcut drawings are amazingly detailed, helpful for seeing mechanical relations, as well as just beautiful.

https://en.wikipedia.org/wiki/De_re_metallica