More than you probably know: Which weighs more, a pound of feathers or a pound of gold?

The pound of feathers weighs more because for precious metals, like gold, the Troy system is used, and a Troy pound is the equivalent of 373 grams:

* https://en.wikipedia.org/wiki/Troy_weight#Troy_pound_(lb_t)

Meanwhile the feathers are measured in the Avoirdupois system, where one pound is the equivalent of 450 grams:

* https://en.wikipedia.org/wiki/Avoirdupois

* https://en.wikipedia.org/wiki/International_yard_and_pound

Now: which weighs more, an ounce of feathers or an ounce of gold? The ounce of gold, because there are 12 troy ounces in a pound, while there are 16 (avoirdupois/'regular') ounces in a (avoirdupois) pound, so the gold would be 31 grams and the feathers would be 28 grams.

See also the difference between the 'international' foot (0.3048 meters) and the US survey foot 1200/3937 meters (a difference of only one one-hundredth of a foot per mile):

* https://oceanservice.noaa.gov/geodesy/international-foot.htm...

* https://www.nist.gov/pml/us-surveyfoot