Answer:
To unravel me you need a simple key, no key that was made by locksmith's hand. But a key that only I will understand.
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.
A device for finding furniture in the dark.
What can go through glass without breaking it?
Each of these ends in a kettle full of precious metal and the double variety is quite awesome
What is always coming but never arrives?