A daft rhyme about shaving a pig for a wig, answered with a very precise count of hairs. The absurdity is the whole point, and children tend to ask for it again just for the pig. Over in four lines.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
Barber, barber, shave a pig.
How many hairs will make a wig?
Four and twenty; that's enough.
Give the barber a pinch of snuff.
About this rhyme
A daft little riddle-joke rather than a true riddle: a barber is asked to shave a pig and work out how many hairs make a wig, then given a joke answer of 'four and twenty' regardless. It only really works read aloud, with the numbers said seriously and the last line landing as the punchline.
Public domain. Text from The Real Mother Goose (Blanche Fisher Wright, 1916), via Project Gutenberg. View the source edition