On the blog Cultural Compass, an employee of the Harry Ransom Center chronicles the discovery of rare evidence of medieval eyeglasses, not in an illustration, but in the end pages of a book.
The blogger writes:
While conducting a survey of manuscript waste found in early printed books I noticed a faint reddish-brown impression of a pair of spectacles on the rear parchment endpapers of a copy of the Opera of Fr. Luigi di Granata.
The spectacles appear to be a pair of leather-framed eyeglasses dating to the late 15th century.