Who was the first person to say the pen is mightier than the sword?

Edward Bulwer-Lytton (1803-1873), in Richelieu (1839) act II sc. 2 has: "Beneath the rule of men entirely great, the pen is mightier than the sWord. " But Cervantes (1547-1616 ) in Don Quixote has: Let none presume to tell me that the pen is preferable to the sWord." And Robert Burton (1577-1640) in Anatomy of Melancholy has: "Hinc quam sic calamus saevior ense patet. The pen is worse than the sWord."