Gold and Feathers

Feather of the same mass as gold has more volume than gold. Therefore the buoyancy of air on feather is more. The apperant weights of the two being equal(1 pound each), the true weight of feather is more.

The feathers. A pound of feathers is measured in avoirdupois weight, in which one pound equals 16 ounces. Precious metals are measured in the troy weight, in which one pound equals 12 ounces.

However, the ounces are not measured in the same way. In avoirdupois weight, one ounce = 437.5 grains. In troy weight, one ounce = 480 grains.

So, one pound of feathers weighs (16)x(437.5 grains) = 7,000 grains. One pound of gold weighs (12)x(480 grains) = 5,760 grains.