It is some while since I first saw this one, and had totally forgotten it

Not to puncture the balloon - it's so charming we _want_ it to be true - but, sadly, it isn't.

http://www.straightdope.com/columns/000218.html
has a nice llittle debunking, and so does Stales.com but unfortunately I don't have the URL handy at the moment...

EDIT: it's Snopes.com, of course. Silly me. Sorry, Stales; take it as a compliment. The full URL is

http://www.snopes2.com/history/american/gauge.htm