The ancient Greek philosopher Anaxagoras (circa 510-428 BC/BCE) was  not a monist. Although his viewpoint seemed to include notions of  the intermingling and basic unity of …ordinary things, his doctrine  of 'nous' (or, mind) as a separate force at work in reality is on  its own an indicator that he did not see the world as monistic.  Still more decisively, he also seemed intent on revising the  monistic teachings of another ancient philosopher, Parmenides. (MORE)

Anaxagoras didn't discover anything but he was the second person in history to suggest that the earth and all of the other planets went around the sun.