In the late 60's, during a lecture by Dai Vernon. The Professor casually pulled a ball bearing out of his pocket. He dropped it onto the bar, demonstrating its solidity and weight, and then without further ado dropped it into a glass of water where much to everyone's astonishment it floated.
Pulling it out of the water, he again dropped it on the bar for examination, and invited the onlookers to attempt to duplicate the miracle.
Only those lucky enough to attend a Vernon lecture during that period in his career got the chance to see it. Thus, over the years, the buoyant ball bearing passed into history.
Comes complete with everything needed to perform, including detailed instructions with hints and tips from some of today's top professionals.