There are a handful of star-shaped sundials known. One, signed "H.F.", is in the British Museum, one is in the Germanisches Museum of uremberg, a 12-point star dial was in the Time Museum collection. In his 1641 treatise on making sundials dialing, Marie Madeleine described a seven-point star dial, although he remarked that the number of points was a matter of choice. In 1708 Welper described a 12-point star dial. A dial with a complicated shape is called polyhedral. Most of them can be used to tell the time from the position of the sun in a number of different ways. Early Renaissance polyhedral dials were made to demonstrate the skill of mathematicians and instrument makers, showing that they had mastered all the new mathematical theories and techniques, while producing a device that actually worked. Later these devices became part of daily life. Sundials work by casting the shadow of a spike called a gn mon onto a series of lines which are calibrated to show the time. Polyhedral sundials showed exactly the same time on all the different faces, no matter what direction the sundial was pointing. Literature: Anthony Turner, Time Museum Catalog.