All these books are free to read: either they're distributed with a free license, or they're in the public domain.
Joseph Frank Payne (editor) and Galen (Author)
Konrad Dietrich Hassler (editor) and Felix Fabri (Author)
Francis W. (Francis Willey) Kelsey (editor) and Marcus Tullius Cicero (Author)
Hector Treub (editor)