If you a photographer in the 1920s, and wanted to snap a picture with some idea of how it would turn out, you had few options. One surefire way was relying on experienced gained through trial and error. Another? Kaufmann's Posographe.
Though it looks somewhat simple and rudimentary, Nathan Zeldes' History of Computing site says that Kaufmann's Posographe is actually a six-variable computer, used to calculate exposure settings based on a handful of conditions.
The input variables are set up on the six small pointers; the large pointer then gives you the correct time. The variables are very detailed, yet endearingly colloquial. For outdoors, they include the setting -- with values like "Snowy scene", "Greenery with expanse of water", or "Very narrow old street"; the state of the sky -- including "Cloudy and somber", "Blue with white clouds", or "Purest blue"; The month of the year and hour of the day; the illumination of the subject; and of course the aperture (f-number).
On second thought, maybe using this thing was kind of awesome for its time. [History of Computing via PetaPixel]