In 1912, Polish-born antiquarian and bibliophile Wilfrid Voynich bought a mysterious illustrated codex hand-written in an unknown writing system that may have been composed in Northern Italy during the Italian Renaissance. The eponymous Voynich manuscript has been studied by many professional and amateur cryptographers, but no one has yet succeeded in deciphering the text. Therefore, it has become a famous case in the history of cryptography.
The manuscript counts about 240 pages in total, but it is assumed that several pages are missing. The text was written from left to right and patterns similar to those of natural languages were revealed by statistical analysis. Still, it was found that the manuscript’s “language” is quite unlike European languages since there are no words with fewer than two letters or more than ten and it seems to be more repetitive than typical European languages. Another difficult aspect is, that the lettering resembles European alphabets of the late 14th and 15th centuries, but the words do not seem to make sense in any language. It was found out that the manuscript probably consists of six sections and except the last one, every section and even almost every page contains various illustrations.
The sections were examined concerning their content and given conventional names. The so called herbal section contains at least one plant on each page, which are not unambiguously identifiable. In the astronomical section, many diagrams can be found with suns, moons, and stars. Further sections are probably of biological, cosmological, and pharmaceutical purpose.
It is assumed that the manuscript was created between 1404 and 1438 and the McCrone Research Institute in Chicago found that the paints in the manuscript were of materials to be expected from that period of European history. It was also suggested that the book originally belonged to Emperor Rudolf II and that at some point, Athanasius Kircher owned the book as well. When Wilfrid Voynich passed away, the manuscript was inherited by his widow and then changed the owners several times before it was donated to Yale University in 1969 where it was catalogued as “MS 408“.
Since the day the examinations on the book started, the first hypothesis considering its author were developed. In a letter to Athanasius Kircher, it was suggested that the author was the Franciscan friar and polymath Roger Bacon. However, this is not the only theory. Many historians came across the name Edward Kelly, who was a self-styled alchemist and claimed to be able to invoke angels through a shewstone and had long conversations with them. The angels’ language was called Enochian, after Enoch, the Biblical father of Methuselah. Several people have suggested that Kelley could have fabricated the Voynich manuscript to swindle the emperor.
In concerns of the book’s languages, many hypothesis came up as well. It was suggested that the text could be a constructed language, others however prefer to believe that “the basis of the script was a very primitive form of synthetic universal language” (John Tiltman). Another theory is called the “letter-based cipher” theory. It suggest that the text contains a meaningful text in a European language, that was intentionally rendered obscure by mapping it to the Voynich manuscript “alphabet” through a cipher of some sort, an algorithm that operated on individual letters. This has been the working hypothesis for most twentieth-century deciphering attempts, including an informal team of NSA cryptographers. Further theories suggest that the text is made of a little-known natural language or that it contains a certain code to be looked up in a codebook.#
The text of the manuscript contains approx. 35,000 “words”. These words have phonotactic characteristics similar to those of a natural language, i.e.,
- a subset of characters can be identified from which one or more characters appear in each word (analogous to the vowels), and
- some combinations of characters never appear.
The statistical analysis of the text reveals further similarities with natural languages:
- the word frequencies obey Zipf’s law,
- the word entropy equals with approx. 10 Shannon/word that of Latin or English, and
- some words appear only on certain pages or in certain sections, others appear everywhere in the text. In particular:
- the “labels” of the illustrations have very few repetitions, and
- in the “herbal section” the first word of each page only appears on this page (perhaps the name of the plant in question).
However, other peculiarities of the Voynich text are nowhere to be found in European languages. For example, there are hardly any words with more than ten, but also hardly any with less than three characters. Furthermore, there seem to be initial and final letter forms, i.e. special forms of characters at the beginning and end of words, as they are common in Semitic languages. And finally, immediate repetitions of the same word or smaller variants appear with unusual frequency.
This theory holds that the text of the Voynich manuscript is mostly meaningless, but contains meaningful information hidden in inconspicuous details – e.g., the second letter of every word, or the number of letters in each line. This technique, called steganography, is very old and was described by Johannes Trithemius in 1499. Though the plain text was speculated to have been extracted by a Cardan grille (an overlay with cut-outs for the meaningful text) of some sort, this seems somewhat unlikely because the words and letters are not arranged on anything like a regular grid. Still, steganographic claims are hard to prove or disprove, since stegotexts can be arbitrarily hard to find. It has been suggested that the meaningful text could be encoded in the length or shape of certain pen strokes. There are indeed examples of steganography from about that time that use letter shape (italic vs. upright) to hide information. However, when examined at high magnification, the Voynich manuscript pen strokes seem quite natural, and substantially affected by the uneven surface of the vellum.
Unfortunately of all the theories, nothing was completely proven and the mystery of the manuscript had quite a cultural impact. Several books, and papers were written about the book itself and also fiction works were published. This includes Russel Blake’s “Voynich Cypher“.
At yovisto academic video search, you may be interested in a video lecture on possible interpretations of the Voynich Manuscript by Stephen Bax.
References and Further Reading:
-  The Unread: The Mystery of the Voynich Manuscript
-  The Voynich Manuscript at the Internet Archive
-  The Voynich Manuscript – The most mysterious manuscripts in the world
-  Athanasius Kircher – A Man in Search of Universal Knowledge, SciHi Blog
-  The Voynich manuscript at Wikidata