This quadrant is calibrated for the latitude of 43? 40', corresponding to Florence. One face is engraved with the hour lines. The hour was indicated with the aid of a plumb-line which allowed the height of the sun at a particular moment to be calculated by indicating the degrees engraved on the limb of the quadrant. The same face bears a magic square ('4 9 2' / '3 5 7' / '8 1 6' totalling 15 in all directions) and the 'Rota medii motus et quantitas diei', which allows the length of the day to be calculated.