Known as the quadrans vetus [old quadrant], this is one of the three surviving medieval quadrants of its kind (the second is in the Museum of the History of Science in Oxford, the other at the British Museum in London). There are two sights on one of the straight sides. The front carries the shadow square, the hour lines, and a mobile zodiacal cursor in its guide, to be positioned for the desired latitude. The back is inscribed with the zodiacal calendar. The instrument displays Gothic characters. Designed to measure heights, distances, and depths, the instrument could also be used as a universal dial. A very similar quadrant is documented in a drawing by Antonio da Sangallo il Giovane [the Younger] (c. 1520?) at the Gabinetto dei Disegni e delle Stampe (Department of Drawings and Prints) of the Uffizi. Provenance: Medici collections.