[silentbicycle]

In Roy Blount Jr.'s Alphabet Juice (under "mnemonic"), he mentions that the ancient Greeks and Romans generally read aloud, even to themselves. (We know this because Julius Ceaser didn't, and his biographers considered his reading silently, and thus more quickly, to be novel. )

[pg]

I'd heard that the first known silent reader was Augustine, though apparently it was his patron, Ambrose.

http://muse.jhu.edu/login?uri=/journals/classical_world/v100...