"white cross" is a fairly common (in Indiana, at any rate) slang term for the stimulant ephedrine. The most common over the counter form of the drug has two indentations on one side which intersect to form a cross. I assume that these grooves are designed to allow easier halving or quartering of a single pill's dose (25mg), but I have never known anyone to bother doing so. Of course, I don't know anyone who uses the substance for its intended purpose either, so this is not terribly surprising.