The invention of the coal torpedo is widely attributed to General Gaberial James Rains WP class of '27. It was simplist of his penchant for "infernal machines". Chunks of coal were sliced in half hollowed out filled with gun powder and glued back together. Smuggled into coal stores and bunkers these bombs did their work indiscrimately. The Sultana is believed to have been destroyed by such a device. Rains served 33 years in the US Army largely in the Infantry. He entered CS service in 1861 and during the Pensula Campaign deployed another invention the "sub-terra shell" the land mine. A cannon shell fitted with a contact primer. He became head of the torpedo bureau at Augusta, Ga in 1864. He there worked closely with his brother Col George Washington Rains the builder of the Augusta Powder Works. General Rains invented a maritime mine by inserting a 5 gal demijohn filled with gunpowder and then inserted into a beer keg first with a contact fuse and later with an electrical device that could be detonated from shore. There was later a "tin can" version. He is also credited by some researchers with the invention of the hand grenade. I don't have a sense of a time line of when Rains did his "tinkering".