1. Get Rails.
2. Loop it around maybe 40x40 like a square.
3. place a minecart in the loop and start go, around, around, around.
4. look to any side and look at the nature, once you turn you will not turn 90 Degrees. The cart will turn 90 Degrees, but ur eye poss will change for each turn >90 degree --> <90 degrees.

Very enejoying, i never noticed this in the beggining, must have been some patch changing it.