The nineteenth century spawned a wealth of peculiar inventions. This website deals (in great detail) with the poison harpoons and lances that were invented at the height of the whaling era. Here's a sample:
In August 1833 an inventor calling himself "Mechanicus" described a hand-darted poison harpoon of his own design in a letter titled, "Sea-Serpent Harpoon" to the editor of the Mechanic's Magazine, and Register of Inventions and Improvements. He explained:
In these days of inventions and of sea-serpents, I deem it meritorious to contrive something for the destruction of such ugly looking monsters as have lately furnished such wonderment to the good people down east. Now, sir, if any of your readers should ever take a notion to go either whaling or sea-serpenting, I would advise them to be provided with some half dozen of the machines of which I send you the drawings.The harpoon was of a two-flued configuration with a narrow hole drilled from the tip to the boss of the shank behind the head, joining a hole through the side of the boss into which was screwed a nipple for a percussion cap. The longitudinal hole through the head was filled with "a proper quantity of some poisonous substance, the effects of which shall be powerful and rapid." The firing mechanism, located in the side of the boss, consisted of a spring-loaded hammer and a two-pronged trigger to hold the hammer cocked. When the iron was darted into a whale, the blubber pressed the trigger back and released the hammer which detonated a percussion cap on the nipple. The explosion forced the poison out of the hole through the head of the harpoon, like a hypodermic needle, to kill the whale.
The poisonous substance used was prussic acid AKA hydrogen cyanide.



