bavarikon4UDescription
This sundial has the shape of a cup with a vertical gnomon in the middle. Its tip forms a small sphere. If the cup is correctly aligned with the help of the compass, then the gnomon’s tip shows the true local time on the lines inside the cup. The network of lines consists of two different time systems. One applies when the cup is empty ("sine aqua"), the other when it is filled ("refractorum aquae"). The Latin inscription already makes it clear that refraction then plays a role: when the light rays pass through the water, they are deflected and therefore end up slightly offset on the inside of the cup.
In another example of a cup sundial by Purmann, reproduced in photographs in the collection of plans at Deutsches Museum, the gnomon can be removed from the cup.
This very unconventional instrument was not made at the imperial court, but in the residence city of Munich. The cup sundial was made of gilded brass in 1602 by the clock and compass maker Markus Purmann (biographical data unknown). Markus Purmann is mentioned in the Munich court chamber records on 7 July 1588 as a clock and compass maker. Later, he apparently also made trumpets, because he appears in the Bavarian court accounts in 1590: "Marxen Purman, compastmachern per ausbösserung der trommeten und macherlon etlicher dazugehörigen mundstückh und andere instrument fl 3.11" (Marxen Purman, compass maker and repairer of trumpets and maker of several associated mouthpieces and other instruments fl. 3.11). In 1590, he made another cup sundial, which is now part of the collection at the Germanisches Nationalmuseum (German National Museum) in Nuremberg. This only works when filled with water: "WHEN I AM POURED FULL: I SHOW THE TIME TO ALL. IF I AM EMPTY THOUGH: IT WILL NO LONGER SHOW".
Perhaps the intention here was to recreate the sundial of King Ahaz mentioned in the Old Testament, in which the shadow went backwards. Sundial makers certainly did always like to demonstrate their ability to construct the hour lines even for particularly imaginative surfaces. Apart from this sundial, Purmann also made sundials in the form of crucifixes, for example, and the Museum of the History of Science in Oxford owns a selection of his works.
According to Kern, similar objects can be found in the Museum of the History of Science, Oxford (Inv. No. 51021) and in the Germanisches Nationalmuseum, Nuremberg. In the lists of secularised instruments in the Bayerisches Hauptstaatsarchiv (Bavarian Main State Archives), only one cup sundial appears under no. 977. It was probably previously in Andechs Monastery. Whether it is identical with this exhibit, however, seems questionable in view of the stated value of just 48 kreuzers.