A neat riddle rhyme that plays on the sound of 'pairs' and 'pears', with twelve knights each taking a pear and a dozen still left hanging. Short enough to recite twice before a child spots the trick.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
Twelve pairs hanging high,
Twelve knights riding by,
Each knight took a pear,
And yet left a dozen there.
Public domain. Text from The Real Mother Goose (Blanche Fisher Wright, 1916), via Project Gutenberg. View the source edition