Here are a couple of stories on the the subject, (from an adjudicator’s point of view.).
From Naval History & Heritage Command:
1)
It has often been claimed that the "brass monkey" was a holder or storage rack in which cannon balls (or shot) were stacked on a ship. Supposedly when the "monkey" with its stack of cannon ball became cold, the contraction of iron cannon balls led to the balls falling through or off of the "monkey." This explanation appears to be a legend of the sea without historical justification. In actuality, ready service shot was kept on the gun or spar decks in shot racks (also known as shot garlands in the Royal Navy) which consisted of longitudinal wooden planks with holes bored into them, into which round shot (cannon balls) were inserted for ready use by the guncrew. These shot racks or garlands are discussed in: Longridge, C. Nepean. The Anatomy of Nelson's Ships. (Annapolis MD: Naval Institute Press, 1981): 64. A top view of shot garlands on the upper deck of a ship-of-the-line is depicted in The Visual Dictionary of Ships and Sailing. New York: Dorling Kindersley, 1991): 17.
2)
The pyramid display of cannon balls was just that, a display, often found in front of the gates of naval and military bases. They were for show only, no one but a blithering idiot would stack cannon balls on a ship. The first time the ship pitched or rolled, the watch on duty would be ankle deep in rolling 18 pound or heavier cast iron spheres. Only 18 pound and heavier cannon balls were kept in racks. Nine pounders and lighter were kept in shot garlands (think hammocks) that were tied to the ships' rails.
So this really leaves it open to interpret the expression. This makes me a fence sitter.
........ Middle of July, wind first stop since leaving Antartica would find us patrolling the fence line in the best cold weather gear the Navy had, WW2 Navy version of an Army great coat called a watch coat, basically a dark blue blanket with sleeves, no lining, we froze and our hut had a small 2 bar heater that was only good for cooking toast on....................... Must admit I do like the snow country, can be quite nice even to running around in shorts at times.............though the area where I live is nice pretty well in shorts for 360 days of the year.
surely Mythbusters would have done something, that may be why I knew...................... The only monkeys I have seen for cannon balls were made of rope and they never left them out in the open anyway, rust like crazy, below decks on a sailing ship in fact even a steel one can be flamin cold either way..............Just remembered I saw the ropes on a base by the ceremonial cannons, a few of us were volunteered to chip and paint the mongrel things along with anything else that didn't move.
