The Astronomicum Caesareum
Printed in Ingolstadt, Germany in 1540 for Emperor Charles V, the Astronomicum Caesareum is considered the most beautiful movable book every made. Peter Apianus (1495-1552), a noted astronomer, included 35 volvelles to show the movement of the planets and their moons. The book is based on the Ptolemaic system where the Sun rotates around the Earth. Its volvelles are actual calculators, astronomical instruments. The book is often referred to as The Emperor's Astronomy.