Answer:
Who works when he plays and plays when he works?
Inside a burning house, this thing is best to make. And best to make it quickly, before the fire's too much to take.
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see.
I am round as a bowl, deep as a tub, but all the world's water couldn't fill me up.
Halo of water, tongue of wood. Skin of stone, long I've stood. My fingers short reach to the sky. Inside my heart men live and die.
It weighs next to nothing but no one can hold it for long. What is it?