Standardized units were known in theory yet very few tools and weights were properly calibrated. The cause for this are corrupt law men who spend nights on end draining ponds so "witches" couldn't drown in it. The witches possessions went to the men that had discovered her guilt (whom promptly took the week off and put the water back in the pond cause their wives didn't like all the water stored in the shed)

The Duck was invented as a way to safeguard against potential false drownings of innocent persons. Lord Bedevere first demonstrated the equivalence of Duck weighting to water-testing to Arthur, King of the Britons. One Duck is roughly the equivalent of 5 kg.