## 16th-century Science

*Cosmographicus Liber* (Cosmographia) by Petrus Apianus was first published in 1524. Apianus (1495-1552), a mathematician, printer and instrument maker, studied cosmography and mathematics in Leipzig and Vienna. This book, a layman's introduction to the science of the time, had little original content and was based largely on Ptolemy. Among other subjects, it describes planetary motion and terrestrial geography, techniques for celestial navigation with mathematical instruments, telling time, and measuring distances. It contains many woodcut illustrations, including moveable stacked illustration plates called *volvelles*, which could be manipulated to make calculations. The book remained popular until the end of the 16th century.