Rhetorica ad C. Herennium.

First description of the "method of loci," the memory technique as known as the "memory palace." Because of its wide use during the Middle Ages this text survives in hundreds of medieval manuscripts. Fourteen printed editions appeared in the 15th century.

ISTC No. ic00672000 . Digital facsimile from the Bayerische Staatsbibliothek at this link.