http://skykam.stumbleupon.com/review/3974853/
Skykam points to a CNN piece on sabotage using items disguised as tiger dung or coal. The coal trick is mentioned here to have been used in WWII, but its origins are actually from the US Civil War. One of these “infernal machines” was used to sink the USS Greyhound, though unfortunately for the saboteurs, the General they targeted was not on the boat at the time.