This is an often quoted "rule" in NM Dan Heisman's Novice Nooks (google for them, they are a treasure trove!!!)
Found it really hard to find the source (Lasker book?) for this ... but I'd easily take Dan's word for it.
The Novice Nooks are filled with principles + exceptions and I'd think this may be exactly what you're looking for.
Here is a link to google book's "Lasker's manuel of chess"
http://books.google.com/books?id=vNXFc-JWpH0C&pg=PA360&lpg=PA360&dq=emanuel+lasker+chess+maxims&source=bl&ots=J7U-vaRNfn&sig=Yhqw22OaMsK51HNLnxdZaH3OpqI&hl=en&ei=A6QzTKurF4L-8AafvNXICw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBwQ6AEwAg#v=onepage&q=emanuel%20lasker%20chess%20maxims&f=false
I found this site with many useful chess principles, where can I find more chess principles? I want to play by the principles.
since I saw Romans video about "no exception" I want to learn more than the principles.
e.g.
"Don't pin the adverse King's Knight to the Queen before the opponent has castled." (One of Lasker's rules)
?? what rules did Lasker have?
http://home.comcast.net/~danheisman/Articles/Dan_sayings.html