Bishop John Wilkins

In 1641, Bishop John Wilkins anonymously authored the book Mercury, or The Secret and Swift Messenger as it was also known. In addition to describing several aspects of cryptography, Wilkins suggested onion juice, alum, ammonia salts, and the "distilled Juice of Glowworms" for glow-in-the-dark writing. Modern invisible inks fluoresce under ultraviolet light and are used as anticounterfeit devices. For example, "VOID" is printed on checks and other official documents in an ink that appears under the strong ultraviolet light used for photocopies.