In today's world, it's often considered impolite to write in books belonging to other people. In the middle ages, however, comments and annotations in the margins were apparently much more acceptable; an aid to future readers.
John Shirley, a scribe for Geoffrey Chaucer, annotated a copy of The Canterbury Tales, sometimes pointing out important parts with the word "Nota" (note), other times explaining obscure references: when Epicurus is mentioned, Shirley writes ".i. deus deliciarum" (that is the god of pleasures). In this case, Shirley was wrong in his identification, but his intent here and elsewhere seems favorable.
In a section of the Knight's tale, Chaucer apparently waxes eloquent on some uninteresting point. Shirley's comment here is, "A Chaucyre pes I prey yowe" (Ah Chaucher, peace I pray you). It's comforting to know that exasperation at the wordiness of medieval literature is such an ancient tradition.