Among the Folger's priceless manuscript treasures is the famous Macro Manuscript, a fifteenth century manuscript which contains the the full texts of three of the four surviving morality plays written in English before 1500.
Without this humble manuscript, we would know little about the once flourishing genre of English morality plays. The last page of The Castle of Perseverance, for example, provides the earliest known stage diagram for an English play. The bottom right corner of the last page of Wisdom contains the ownership statement of the monk Thomas Hyngham, which in English reads: "O book, if anyone should . . . ask to whom you belong, you shall say, I belong above all to monk Hyngham."
Detailed copy information may be found in the Hamnet record. Links to full-text "Bookreader" images of the Macro Manuscript may be found at the end of that record.