Units of paper quantity of 480 sheets, now known as a 'short' ream. Reams of 472 and 516 sheets are still current, but in retail outlets paper is typically sold in reams of 500. As an old UK and US unit, a perfect ream was equal to 516 sheets. Certain types of specialist papers such as tissue paper, greaseproof paper, handmade paper, and blotting paper are still sold (especially in the UK) in 'short' reams of 480 sheets (20 quires of 24 sheets). However, the commercial use of the word 'ream' for quantities of paper other than 500 is now deprecated by such standards
How many angels can dance on the head of a pin? about how many could perch at the same time on the head of a pin"". Dorothy L. Sayers argued that the question was "simply a debating exercise" and that the answer "usually adjudged correct" was stated as, "Angels are pure intelligences, not material, but limited, so that they have location in space, but not extension." Sayers compares the question to that of how many people's thoughts can be concentrated upon a particular pin at the same time. She concludes that infinitely many angels can be located on the head of a pin, since they do not occupy any space there: