How we know what we know about history: annotation.
"Certainly an unfortunate computer, Copernicus was a still more unfortunate geometer, and so failed to do what Ptolemy failed to do, but made even more mistakes. Butwe shall complete what was left undone and we shall correct the mistakes in the French tables, in which we shall also demonstrate the Prutenic computations of the heavenly motions through the use of models which they call Apollonian, but if these models are less pleasing, through the use of Ptolemaic models released from motion with respect to an improper centre and the hypocenters or inclinations of the epicycle."
Viete, 1600.