Caption:
Refining of silver, showing (2) a test put into the furnace and (3) burning the silver in a test. A test warming (8) and a roaster for making burnt silver dry (9). From 1683 English edition of Lazarus Ercker "Beschreibung allerfurnemisten mineralischen Ertzt- und Berckwercksarten" originally published in Prague in 1574. Copperplate engraving. (Photo by: Universal History Archive/UIG via Getty Images)