That's actually how traditional weights and measures used to work. Tithes and taxes owed to the lord were set out in age-old contracts that even the lord couldn

That's actually how traditional weights and measures used to work. Tithes and taxes owed to the lord were set out in age-old contracts that even the lord couldn't change, with things like "ten pounds of grain" written in the contract. But the lord controlled the legal measures and would adjust the length of a foot, volume of a gallon, and weight of a pound as suited the conditions. The measurements would consequently vary between one feudal domain and the next, as well as over time. This is why the metric system, which promised standardized, invariant, and universal measures, was hailed as a win for the people during the French Revolution.