The group of canoers have all got their boats sorted, kit stowed and are impatiently waiting to get underway. One of their number, however, has emptied a huge bag of assorted types of headgear onto the ground. He picks one up, carefully examines it inside and out, and mumbles to himself, "six and five eighths". He then repacks the hat into his bag before picking up another one. He examines this one just as carefully and mutters "seven and a quarter!". He selects the next one, and the next, and the next, each time scrutinizing it meticulously before deciding on a number. This goes on for 10 minutes, and his mates are getting fed up. "Come on," says one, "We're all waiting for you. What do you think you are doing, anyway!"
"Just erring on the side of caution." he replies, "I'd sooner do all my cap-sizing on dry land!"