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I thought it was from Journey to the West or Tales from the water margin? Maybe even Romance from the 3 kingdoms?
old xia novels. But hey, it makes sense because those and others were eventually...

Originally it was a tool. Just a shovel.
However, it is fair to say that it's been around at least since the 1600's where it appears in story telling at the very least as the Yueyachan (the crescent...

http://www.martialartsmart.com/45-84cs.html

says it's only 14 pounds.... but I suspect that weight varies a little from piece to piece.