Actually, I think the device in question is a spinoff from another device used in the medical industry for colonic inspections. Since
death-by-lava-enema is an extremely restricted market, I don't believe a patent was accomplished.
There are similar instances of low-tech approaches to similar solutions throughout history. One Roman soldier, for his punishment for some crime, was forced to imbibe molten silver ... which as you can imagine, killed him. In fact, making prisoners drink molten metal has happened more than once, to wit:
http://www.folger.edu/html/newimages/INS0072.jpg
And introductory text for it:
"The widely circulated woodcut first published in Theodor de Bry's America Pars Quarta (1594), is surely the boldest restatement of the topos. In this strikingly graphic representation, probably crafted by the Huguenot artist Jacques Le Moyne de Mourges, vindictive Amerindians lay exemplary punishment upon captured Spanish soldiers, forcing them to drink the molten gold they so shamelessly coveted, literalizing their appetite for the precious metal in such a way as to provide the Iberians their poetical just deserts."