Horses + Stairs = X-Ray Glitch

I was riding a horse and my head went into a stair and it let me see through all the blocks. It only works with the regular stairs (that aren't upside-down) and your head has to be in the lower part of the stair, the part that is basically a halfslab.

Another way to reproduce this is to use a piston to push a stair into you head and sneak at the exact time you flip the lever to activate the piston. If you did it right, you can let go of the sneak control and you won't actually stop sneaking (i.e. you won't rise back up).