[webnrrd2k]

Speaking of mixed units, don't forget the alwys fun distinction of avoirdupois pound vs troy pound...

People sometimes ask "what's heavier, a pound of feathers or a pound of gold?", the implication is that you're stupid for for asking a dumb question. The technically correct answer is that the pound of feathers is heavier. The expected answer is usually that they're the same weight, because there is no difference in weight between the two things that both weigh a pound. The problem is that, in the USA, a pound of feathers is measured with the avoirdupois pound, while a pound of gold is measured in troy pounds. The troy pound is lighter than the avoirdupois pound, so the answer is that a pound of feathers is heavier.

While a troy ounce is heavier than the avoirdupois ounce, and the grain unit is equal in both. So, depending on whether you ask for a pound/ounce/grain, the answer can change. https://en.wikipedia.org/wiki/Troy_weight