Shelley discusses the Don Juan and asks Trelawny to procure him a small quantity of prussic acid. ‘I need not tell you I have no intention of suicide at present’, he assures him, ‘but I confess it would be a comfort to me to hold in my possession that golden key to the chamber of perpetual rest. The prussic acid is used in medicine in infinitely minute doses; but that preparation is weak, and has not the concentration necessary to medicine all ills infallibly—A single drop, even less, is a dose, and it acts by paralysis.’ Shelley was then suffering from periodic but excruciating pain, possibly as a result of kidney stones.