Schaefer supported his theory with history and toxicology. He deduced that Cleopatra -- who wanted suicide and was reputed to want a quiet and pain-free death -- did not die of a cobra bite. A bite from a cobra is not always fatal and quick; instead, its victim endures a horrible death. Schaefer and German toxicologist Dietrich Mebs decided that Cleopatra might have used a mixture of hemlock, wolfsbane and opium. Opium can make a person fall into a quiet, deadly sleep.