During World War II, in an effort to cut down on the use of fuel, England's King George VI issued a curious edict: bathtubs in Buckingham Palace and Windsor Castle were to be filled with no more than five inches of water.
In order to make the "level of his commitment" unequivocally apparent, the king had lines painted at the appropriate level.
Sources
M. Driscoll, ed., 5087 Trivia Questions & Answers
