The Copiale cipher is an encrypted manuscript consisting of 75,000 handwritten characters filling 105 pages in a bound volume. Undeciphered for more than 260 years, the document was decrypted in 2011 with computer assistance. An international team consisting of Kevin Knight of the University of Southern California Information Sciences Institute and Viterbi School of Engineering, along with Beáta Megyesi and Christiane Schaefer of Uppsala University in Sweden, found the cipher to be an encrypted German text. The manuscript is a homophonic cipher that uses a complex substitution code, including symbols and letters, for its text and spaces.

Previously examined by scientists at the German Academy of Sciences at Berlin in the 1970s, the cipher was thought to date from between 1760 and 1780. Decipherment revealed that the document had been created in the 1730s by a secret society called the "high enlightened (Hocherleuchtete) oculist order" of Wolfenbüttel or Oculists. The Oculists used sight as a metaphor for knowledge.