100
The best storage method devised was a square-based pyramid with one ball on top, resting on four resting on nine, which rested on sixteen. Thus, a supply of 30 cannon balls could be stacked in a small area right next to the cannon. There was only one problem...how to prevent the bottom layer from sliding or rolling from under the others.
The solution was a metal plate called a 'Monkey' with 16 round indentations. However, if this plate were made of iron, the iron balls would quickly rust to it. The solution to the rusting problem was to make 'Brass Monkeys.'
Few landlubbers realize that brass contracts much more and much faster than iron when chilled. So... when the temperature dropped too far, the brass indentations would shrink so much that the iron cannonballs would come right off the monkey.
What is "Cold Enough to Freeze the balls off of a Brass Monkey"?