Answer:
When set loose I fly away. Never so cursed as when I go astray.
Two bodies have I, though both joined in one. The more still I stand, the quicker I run.
A shimmering field that reaches far. Yet it has no tracks, And is crossed without paths.
This only turns over once you have travelled very far. What is it?
A harvest sown and reaped on the same day in an unplowed field. Which increases without growing, remains whole though it is eaten within and without. Is useless and yet the staple of nations.
As round as an apple. As deep as a cup. All the king's horses can't pull it up.