A rope

In ancient China, the emperor sometimes sent a piece of yellow fabric to people, that mean, go kill yourself by hanging your neck with this piece of nice silk. I sometimes wonder why people at that time would submit to this absolute powerful and never thought about running away. I think the reason is that it would be an easier way to die without too much pain. Otherwise the emperor has the power to throw you into the boiling oil or slice you into thousand pieces (one of the most cruel punishment, the executor would be guilty if the person die before he finished cutting a thousand pieces of meat off). Cruelty is the way to mind-control the crowd, I guess.