Feivel (& oomis1105),
According to the shitta on WikiAnswers:
While on the face of it a pound of feathers would seem to weigh the same as a pound of gold, this overlooks the fact that gold is universally weighed using a different definition of ‘pound’ than that used for most other materials.
Precious metals such as gold are measured in troy weight. A troy pound is 12 troy ounces, and each troy ounce is 480 grains, making a total of 5760 grains to the pound of gold.
Most materials use pounds and ounces from the avoirdupois system, and such a standard pound is made up of 16 ounces, where each ounce is 437.5 grains, making a total of 7000 grains to the pound of feathers.
All this means that a “pound” of feathers (or bricks, or lead) is heavier than a “pound” of gold.