Convincing my students that the way they stemmed note heads when writing music mattered is something I remember doing repeatedly. I would say up-right, down-left (in the same way one says “righty-tighty, lefty-loosey”) to help them remember the rule.
So I did a double take when I came across this displayed on a monitor at the Globe Theatre in London back in December of 2005:
Now it might be a historically correct representation of notation during Shakespeare’s time. I never ended up researching that, or printing it out to show students. I’m pretty sure my intention in taking the photo was to show it to the next student who brought me theory homework incorrectly stemmed (but you know what they say about good intentions…).