How to Signal
One of Denmark's most loved artists, Storm P., wrote a satirical book with drawings called "For Cyklister" - For Cyclists - back in 1934, wherein he took the piss out of the bike culture.
The text under this drawing goes like this:
"Lets' say that you have to turn left. Extend your hand – be careful that it can't be seen – to the right... that means you're NOT going that way."