How many footprints does an ox leave in the last furrow it plows?
An ox plows a field all day, back and forth, furrow after furrow, pulling the plow directly behind it. In the very last furrow it plows, how many of the ox's own footprints are left behind?
Reveal the answer
None. The plow, dragged immediately behind the ox, destroys each footprint the instant it's made. This riddle is Problem 14 of the Propositiones ad Acuendos Juvenes ('Problems to Sharpen the Young'), a set of brain-teasers compiled around 800 AD and traditionally attributed to Alcuin of York, tutor to Charlemagne.
— Alcuin of York (attrib.), Propositiones ad Acuendos Juvenes — Problem 14, c. 800 AD