The "wine", "fluid", or "liquid gallon" has been the standard US gallon since the early 19th century. The wine gallon, which some sources relate to the volume occupied by eight medieval merchant pounds of wine, was at one time defined as the volume of a cylinder 6 inches deep and 7 inches in diameter, i.e. . It was redefined during the reign of Queen Anne in 1706 as 231 cubic inches exactly, the result of the earlier definition with π approximated to . Although the wine gallon had been used for centuries for import duty purposes, there was no legal standard of it in the Exchequer, and a smaller gallon was actually in use, meaning this statute became necessary; it remains the US definition today.