Agreed -- no solvent, ever, anywhere on a Powerbook!
How big is the bit of wax? If it's tiny, try blowing warm air on it to soften it. Perhaps -- PERHAPS -- a blow dryer on a low setting, held at least 12" away from the screen, would also work. When it's softer, it should be easier to remove. Gently wipe away with a non-abrasive cloth or tissue (make sure it's not one of those tissues that has lotion in it).
If there's a remaining smudge, use an LCD cleaner. Try not to spread the wax around, though, of course. I have a cleaner by 3M: it's a little spray bottle and a tiny shammy. I think I got it at Best Buy, but I've seen it other places, too. I wouldn't recommend using anything other than an LCD cleaner.
Anyway, take my comments for what they're worth, because I've never actually had to clean wax off an LCD. (Thankfully! 😱 😛 )