Answer:
Large as a mountain, small as a pea, Endlessly swimming in a water-less sea.
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.
You can tumble in it, roll in it, burn it, animal eat it. Used to cover floors, still used beyond stall doors. Freshens whatever it is placed on. Absorbs whatever is poured into it.
It cannot be seen, cannot be felt, Cannot be heard, cannot be smelt. It lies behind stars and under hills And empty holes it fills. It comes first and follows after, Ends life, kills laughter.
A beggar's brother went out to sea and drowned. But the man who drowned had no brother. Who was the beggar to the man who drowned?
I can only be played on a windy day