In the Stargate SG-1, S1 episode The Torment of Tantalus, they gate to a planet which had an ancient meeting place of The Four Great Races.
The races had there some compendium of knowledge, which Daniel figured had to be worth a LOT of scientific interest.
At the end of the episode, they try dialing back to the planet, but cannot get through, presumably because the gate has fallen into the ocean.
Once the SGC had access to space craft, is there any indication of them having ever made a visit back to this planet, to try to recover the database of The Book?