In 16th century, there was a city wall of Amsterdam, the Waag was one of the gate which called St. Antony's Gate. This 1488 constructed building was converted as Weigh House in 17th Century.
In the common practice, many of weigh houses were built at the gate or boundary of the city. The purpose was to weigh the import or export goods and set the rate of tariff.
Besides the purpose in customs or excise, it was also used to determine some people who was suspected as a witchcraft.
If the weight of a person was lighter than the standard, he or she was classified as witchcraft. This function was active in 1550 - 1690.