Catholic Church [Liturgical miscellany]
[Italy, between 1450 and 1499]  Parchment
Ms. Codex 1248 f. 122r    University of Pennsylvania
Bottom of image was digitally reconstructed.

The Guidonian hand, a tool attributed to the 11th-century musical theorist Guido d'Arezzo, (991/992 – after 1033) was used from the 12th through 16th centuries for teaching sight-singing.