Pound (mass) for the weight of certain precious metals, especially in the trade; these are normally quoted just in ounces (e.g. "500 ounces") and, when the type of ounce is not explicitly stated, the troy system is assumed. Historically, the pound sterling was a Tower pound of silver. In 1528, the standard was changed to the Troy pound. The avoirdupois pound, also known as the wool pound, first came into general use c. 1300. It was initially equal to 6992 troy grains. The pound avoirdupois was divided into 16 ounces. During the reign of Queen Elizabeth, the avoirdupois pound was redefined as
How many angels can dance on the head of a pin? How many angels can dance on the head of a pin? The question "How many angels can dance on the head of a pin?" (alternatively ""How many angels can stand on the "point" of a pin?"") is a reductio ad absurdum of medieval scholasticism in general, and its angelology in particular, as represented by figures such as Duns Scotus and Thomas Aquinas. It is first recorded in the 17th century, in the context of Protestant apologetics. The question has also been linked to the fall of Constantinople, with the imagery of scholars debating about minutiae while the Turks besieged the