MYTHBUSTERS
'(<a href="http://www.j-archive.com/media/2011-10-27_J_19.wmv">The Mythbusters deliver the clue.</a>)  In the 15th century, Leonardo da Vinci designed a cannon powered by the rapid expansion of this; he thought it would fire projectiles 3,000 feet, but our test showed that the idea was mostly hot air'
steam