One of the weirdest measurements is a bushel, which can vary according to what is being measured. I came across a letter where American Quakers are writing home to their Irish relatives, saying (as far as I can remember) that they had dug and clamped two bushels of potatoes, which would be enough for the family for a year.
Given that at this stage (the book with the quote, Them Wild Woods, contains letters sent from the 18th century to the late 19th century) an Irish farmer would eat two stone of potatoes a day, that must have been plenty of potatoes - but how much?