Heindrick Sneewins, the maker of this Dutch circle, in 1643 moved from Rotterdam to Leiden. He most probably had two brothers, both instrument makers too: Johan in Utrecht and Antoni in Delft. Hardly anything is known about them except that they all three were extremely proficient. Their products nowadays are very rare. The Dutch circle was used during land surveys and is also known under the name of circle of Dou, after its inventor Jan Pietersz Dou. Dou was licensed surveyor of the district of Rijnland in the province of Holland, named after an old branch of the river Rhine and with Leiden as its main town. For mapping out the land surveyors generally used triangulation, a method inventend in 1533 at the university of Leuven (Louvain) by Jemme Reinersz, better known as Gemma Frisius (December 9, 1508 – May 25, 1555), from the Frisian town of Dokkum. In 1608, when lake Beemster, north of Amsterdam, was reclaimed with Amsterdam finance, Dou used the Dutch circle for the first time. [source: Boerhaave Museum, Leiden]