The "without wax" meaning for "sincere" is a complete myth. I don't know where the myth came from - probably a clever "reverse etymology" that someone invented for fun - but its current popularity is no doubt due to its use (and presentation as a "fact") in a
Dan Brown novel. It has no basis in fact.
http://www.etymonline.com/index.php?term=sincerehttp://www.etymonline.com/index.php?term=sincerity
~Chrisell~
Proudly Australian
www.archaeochrisell.blogspot.com