Guido Aretinus: Micrologus, Regulae rhythmicae (Fragment)
A fragment of an eleventh-century Latin music treatise by Guido of Arezzo, the Micrologus, copied in ink on parchment for monastic and clerical readers in the Swiss manuscript collection. The picture shows a small diagram of a circle with a cross and surrounding Latin words in brown ink, with a column of letters at the right edge, and a designer could take its spare, hand-lettered diagram layout as a model for annotated charts.
