Definition:Bourbaki Dangerous Bend Symbol

Definition
The Bourbaki dangerous bend symbol is a symbol invented by the to warn the reader that there exists the serious possibility of making a common mistake while interpreting or utilising the material presented.

It was originally presented by, as the pre-$1949$ French traffic road sign:
 * Dbend.png

Variants exist, notably 's version:
 * Dbend-knuth.png