Petrus Apianus, Astronomicum Cæsareum

Petrus Apianus, the son of a shoemaker, was an acclaimed German astronomer and printer. This beautifully produced book, his most famous work, contains a series of rotating paper discs, known as volvelles, mimicking the planets’ movements. This volvelle shows how to determine the Moon’s latitude, and can be spun round to point at the various signs of the Zodiac. The volvelles could also be used to cast horoscopes: at that time, astronomy and astrology were not regarded as separate disciplines. Shown here: ff. 21v–22r