I copied this off of a post at http://twodollarbill.us of all places.
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Q. Which weighs more, an ounce of feathers or an ounce of gold?
A. The ounce of gold, because:
* gold is weighed by the troy ounce (31.10 grams), and
* feathers are weighed by the avoirdupois ounce (28.35 grams).
Q. Which weighs more, a pound of feathers or a pound of gold?
A. The pound of feathers, because:
* there are 16 avoirdupois ounces in an avoirdupois pound, totaling
453.60 grams of feathers, but
* there are only 12 troy ounces in a troy pound, which works out to
373.20 grams of gold.
