Answer:
Lighter than feather and softer than silk, yet the strongest man in the world cannot hold me for more than a few minutes. What am I?
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair.
I am Invisible Man's drink at snack time
I am an instrument capable of making numerous sound but cannot be touched or seen.
I tell people to be careful when handling boxes.
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.