Who invented cocoa powder?

It was originally a bitter chocolate drink drunken by a king of the Mayhams (SP? I'm not sure if that was it or who they were) But the king would drink lots of glasses of it every day, and soon I guess they experimented and added sugar. I'm sorry that I don't have all the info.

The actual cocoa comes from Cocoa tree that when cracked open reveals the cocoa beans that chocolate is made from.