10 ingots weighs 1 stone 6 ingots weighs less than 1 stone, but due the fractions not being invented yet on Sosaria, they also weigh 1 stone...but we all know they weigh less than a stone. A blacksmith needs 6 ingots to create a short spear. 6 ingots that weigh less than a stone. a Short spear weighs 4 stones. It's obvious, you know.
Pff that's nothing. The average Renaissance torso weighs 2 stones. Chop it up, and you're left with a rib cage and a heart (or liver), which in total weighs 6 stones. How's that for UO math.