Mensuration.- Zobel (Johann G.) and J. Muller. Beschreibung einer Flächen-Berechnungs und Theilungs-Maschine, Munich, Joseph Lindauer, 1815.

Mensuration.- Zobel (Johann G.) and J. Muller. Beschreibung einer Flächen-Berechnungs und Theilungs-Maschine, 3 folding engraved plates, later boards, a little chipped, preserved in custom drop-back box, [Tomash & Williams Z9], 4to, Munich, Joseph Lindauer, 1815.

? Rare.

"Nothing is known of the authors other than that Zobel had the title of trigonometer to the king and was apparently working for the Bavarian tax authorities while Müller was a mechanical craftsman who built the instrument described here.

When Bavaria was attempting to reform its tax system it became obvious that the existing land surveys were out of date and that the measurement of irregular plots of land was the root of the problem of creating accurate assessments. This problem was remedied by a new survey and the use of an integrating machine to determine the areas. The machine apparently worked by dividing irregularly shaped plots into small slices whose areas could then be easily added up. This is essentially an analog of the mathematical procedure known as Simpson's Rule for integrating functions." - Tomash & Williams.