Rapidly drawn and annotated by the Renaissance sculptor, painter, architect, and poet Michelangelo Buonarroti, this simple drawing provides the height, width, and depth of a rectangular marble block in Florentine braccia (a unit of measurement). The diagrammatic sketch was made by the artist to order forms of marble from the quarries of Carrara and Seravezza in the Apuan Alps of western Tuscany. Michelangelo would have requested this stone for his architectural and sculptural renovations of Florence’s Cathedral of San Lorenzo and the New Sacristy, which commenced in 1519. This sheet was presented by Cosimo Buonarroti—a nineteenth-century descendent of the artist—who, in 1842, certified its authenticity with a handwritten note on its verso.