Claudius is thought to have been murdered using this mushroom, or one closely related to it. They're mild tasting and are actually in the same genus as the so-called Caesar's mushroom, which is so tasty that it was a favourite of Roman emperors, as the name suggests, so it would be easy to sneak some into a mixed dish without them being noticed. Apparently the dose he ate wasn't quite fatal, so while he was horribly ill his personal physician (who was in the pay of Agripinna and Nero, i.e. his wife and stepson) administered a "cure" that was actually henbane or something, which finished him off.