The night after the murder of Clodius Eprius, Gaius Tero and Kleandros had dinner together to discuss the strange mysteries in his death. During the discussion of how to speed a lead button fast enough to smash through Eprius' skull, Kleandros recalled a famous artificer from the previous generation named Heron son of Ktesibios from Alexandria. One of his devices was a cauldron with a hollow ball on its lid. The ball had a tube from the cauldron on one side and a pivot on the other. It also had bent nozzles around its circumference. When the cauldron was heated, steam would fill the ball and escape through the nozzles causing the ball to spin. If some way could be found to block the steam for a while and then release it at once, then it could give a small pellet of metal a very strong push