"There are considerable complexities attached to other measures. It is not so much that they vary as they may be differently interpreted, according to what you are trying to measure. A foot in length is the same as your modern foot of 12 inches but if you are measuring cloth you use the ell, normally 45 inches--but 27 inches if the cloth is Flemish. Probably the most complicated measures are those involving liquids. A gallon of wine is not the same volume as a gallon of ale. A standard hogshead contains 63 wine-gallons or 52.5 ale-gallons. Except that there is no such thing as a standard hogshead; there is a standard for wine, another for ale, and a third for beer (which is imported). If you are buying beer in London, a hogshead amounts of 54 ale-gallons; if you are buying ale, it amounts to 48."
And so on.
https://books.google.com/books?id=NF_8YUhO7CUC&printsec=fron...