I was playing Quelf with the kids. I received the question, “Which weighs more? A pound of feathers or a pound of gold?”
Quelf’s answer was, “Neither. They both weigh a pound.”
Wrong answer, Quelf! The feathers weigh more.
Gold and other precious metals are weighed in troy pounds. A troy pound is 12 troy ounces. A troy ounce is 480 grains.
Feathers and pretty much everything else that is not a precious metal or gemstone are weighed in avoirdupois pounds. An avoirdupois pound is 16 avoirdupois ounces. An avoirdupois ounce is 437.5 grains.
Both the troy and avoirdupois systems use the grain defined by the International Yard and Pound Agreement of 1959—a grain is equal to 0.06479891 grams.
A 12-troy-ounce troy pound weighs 5760 grains (480 grains × 12). A 16-avoirdupois-ounce avoirdupois pound weighs 7,000 grains (437.5 grains × 16).
So, a pound of gold weighs 5,760 grains and a pound of feathers weighs 7,000 grains and the pound of feathers is heavier.
Of course, Quelf could have used a kilogram and everything would have worked out fine.