Sho-Shogi, or Small Shogi was the game that led to Modern Shogi. This game didn't allow drops like modern Shogi, but had an interesting piece called the Suizo (酔象).  It moved like a Ousho (王将) but couldn't move to the space directly behind it.  This piece upon promotion became the Crown Prince (太子) which then became a second King (王将) in all ways.  So if that happened, you had to capture one and checkmate the other to win.  

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- It is said the Emporer (I'll have to check which one...)had the Suizo (酔象) piece removed and the ability to drop pieces back onto the board added.  Which made it into Modern Shogi.