Blind Fold Drive Bag - X-Ray

A black bag is handed to a spectator who is asked to place it over their head. They attest they can see nothing but black- no light at all. The magician then takes the bag and places it over his/her head and asks the spectator to write anything (perhaps on a large dry-erase board). The magician is able to write the exact same thing- he must have X-Ray vision!