All you need is snow, a piston and a pushable block.

no

don't

DON'T

You put snow on the floor in a straight floor.

Break a block right next to the snow.

Break 2 more, in line with that one.

Put the piston and block in place.

Should be empty space, block and piston in a straight line.

Put a lever next to the piston.

Enter the hole.

does that work in bedrock?

hehe

Crouch and use the lever.

The block should push you into the snow.

And you'd have a poor but useful x-ray.

Dunno, but mayhaps it does.

I can confirm that it doesnt

You don't go into the crawling state in bedrock