A rare collection of medieval manuscripts and autographed books from the library of Charles Sumner is on exhibition in the Treasure Room of Widener Library. One of the most interesting exhibits is the Greek exercise book used by John Dryden while a student at Westminster school. The fly-leaf bears the famous author's signature in a childish hand. A large Bible bearing on its fly-leaf the signature of John Bunyan and a copy of Pindar with marginal notes by John Milton are on exhibit, as is a ponderous copy of the Nuremberg Chronicle with woodcuts by Michael Wolgemuth and Wilhelm Pleydenwurff. Among the manuscripts, which are mostly Greek, Latin, and Hebrew texts copied in the middle ages, is one done by the monk Erasmus, with marginal pen and ink drawings by Holbein.

There is also on exhibit in the Treasure Room a collection of books about the founding and early history of Harvard College. The collection includes the only known extant volume from the library of John Harvard.