The comment you link to almost certainly references Hero ( or Heron) of Alexandria, who described a number of steam-powered devices in his 1st c. AD writings, some of which were supposed to do ceremonial tricks. A steam-powered throne is not among them, though. You could imagine something fairly simple being done with water- if there was a tank below the floor, the throne was sitting on a post mounted on something that would float in the tank, and water was let into the tank, the throne would float, and so also rise.

I have heard this rising-throne story in connection with the famous account ( or legend) of the Kievan Rus sending delegations around to various countries, in order to decide what religion they should all follow; the Byzantine Emperor impressed them with his magic tricks, so they became Greek Orthodox. But that's wrong- the rising-throne is not mentioned in The Primary Chronicle of Nestor, which has that famous account. So, I can't help you there.