The humble paper clip hold a surprising link to the Cold War era. During the height of espionage, the lowly paper clip was used as a covert communication tool by spies.

Because of its simple and unobtrusive nature, a paper clip could be discreetly bent into a coded shape and passed between agents carrying secret messages.

Prompt:
What seemingly mundane everyday object has a surprising historical connection to royalty, espionage, or a dangerous natural phenomenon?