Scytale - Ancient Spy Gadget - Early Tweet

500 BC: The Spartans of ancient Greece invented the Scytale to transport hidden messages. Scytales were long, slender rods typically wrapped in a thin strip of papyrus, leather, or parchment.

A message was written on the wrapping, and then the strip was unwound and passed on to a messenger. Only when it was rewound around a rod of the same diameter could the original message be deciphered. (more)