In the marble walls as white as milk, Lined with skin as soft as silk, Within a fountain crystal clear, A golden apple does appear. No doors are there to this stronghold Yet thieves break in and steal the gold.
A man wants to get into a night club where the bouncers test each person before they can enter. The man waits and watches. A woman walks up to the bouncers and the bouncers say 6. The woman replies with 3 and goes in. A small man walks up and they say 12. The man replies 6 and is admitted. The first guy thinks he’s figured it out and walks up. They say 4 and the man replies with 2, but they don’t let him in.
Water. As ice I’m hard and cold, as water vapor I’m hard to hold and I’m always present in the air as humidity (aka water vapor). If the earth ever runs out of water, we’re toast.