Trebuchet03 writes – “The first steam engine was invented by Herron of Alexandria around 150BC (actual date is unknown — that whole Alexandrian library arson thing :/ and books disagree on dates). The history channel (or was it discovery) called this person Mechanos – I’m not sure where that name came from, but it fits :P
So basically, it is a sealed pressure vessel with steam outlets. Hot steam is pumped in (or generated within) and the steam outlets provide a torque based on their perpendicular component to the radius of rotation. You also need some sort of bearing to allow for rotation ;)
Well, pressure vessel could be a fancy name for soda can….” – Link.
Building a simple Hero’s Engine from a soda can – Link.