 The case of Claudius ' poisoning is more complex . Claudius was known to have been very fond of eating Caesar 's mushroom . Following his death , many sources have attributed it to his being fed a meal of death caps instead of Caesar 's mushrooms . Ancient authors , such as Tacitus and Suetonius , are unanimous about poison having been added to the mushroom dish , rather than the dish having been prepared from poisonous mushrooms . Wasson speculated the poison used to kill Claudius was derived from death caps , with a fatal dose of an unknown poison ( possibly a variety of nightshade ) being administered later during his illness . 
