Approximate measures
Unregulated volume units still in use / From Wikipedia, the free encyclopedia
Approximate measures are units of volumetric measurement which are not defined by a government or government-sanctioned organization, or which were previously defined and are now repealed, yet which remain in use.[1][2][3]
It may be that all English-unit derived capacity measurements are derived from one original approximate measurement: the mouthful, consisting of about 1ā2 ounce, called the ro in ancient Egypt (their smallest recognized unit of capacity).[4][5] The mouthful was still a unit of liquid measure during Elizabethan times.[6] (The principal Egyptian standards from small to large were the ro, hin, hekat, and khar.)[7]
Because of the lack of official definitions, many of these units will not have a consistent value.