It is always intriguing when some mystery from the far distant past outfoxes the tools and methods of modern investigators to hold onto its secrets. The most celebrated is the Shroud of Turin, long considered by many to be the burial cloth of Jesus. Although carbon-14 dating indicates it is only a few hundred years old, no one has come up with a credible explanation of how the negative image of Jesus could have been placed on the cloth by medieval hoaxsters.

A much more obscure mystery resides in the library of Yale University, writes Bradley E. Schaefer in the November issue of Sky & Telescope. The Voynich Manuscript has successfully defied scholars and code-breakers down through the centuries. Its age, purpose and writing are as much a mystery today as when it first surfaced nearly four centuries ago.

Schaefer became interested in the Voynich Manuscript when he read David Kahn’s 1967 book, “The Codebreakers,” as a seventh-grader. The manuscript, which Kahn calls “the most mysterious manuscript in the world,” consists of about 204 pages, measures 6 by 9 inches, and is constructed of vellum. Kahn describes the pages as being bordered with dozens of tiny female nudes, astrological symbols, and more than 400 detailed drawings of plants in vivid shades of blue, red, yellow and green.

The writing, at first glance, is deceptively like most languages. The symbols appear to be mild variations on letters of the time, the writing flows smoothly as if being copied by a scribe from another text, and groups of symbols appear in regular patterns. It seemed to be a simple rewriting of some known language into a code of the author’s own devising and, as with many others, fairly simple to break. But appearances, at least in this case, were highly deceptive.

The manuscript’s recorded history starts in 1666, when Joannes Marci of the University of Prague sent it to a famous Jesuit scholar named Kirchner for deciphering. Kirchner, who had already written a book on cryptology, assumed it would be a simple task but could not break the code. His failure was followed by countless others as the manuscript traveled around Europe.

The manuscript’s modern saga begins in 1912, when it was bought by a rare book dealer named Wilfred Voynich from a Jesuit school in Italy. Voynich shared copies of the manuscript with anyone who seemed likely to solve it. At first, botanists hoped to match words with the plant illustrations, but, even though they were extremely detailed, none of the drawings were of actual plants. They were all imaginary! Astronomers hoped to match the drawings of star groupings with names, but this came to nothing.

In 1919, William Newbold, who did cryptography work for the U.S. government, claimed to have cracked the code using anagrams, but this was proved erroneous in a lengthy research article published in 1931 by a member of Britain’s MI-8. In 1944, a group of government code-breakers tried their hand at it but could only surmise that it was some kind of artificial language like a computer machine language.

Dr. Theodore Peterson of St. Paul’s College spent 40 years studying the manuscript before giving up, saying it was likely some kind of medieval shorthand. Schaefer says that even the National Security Agency could not break it. Voynich died in 1930 without learning the secrets of his mysterious manuscript.

So what is the secret of the manuscript? Marci thought that the manuscript was written by Roger Bacon, a 13th century English friar who was hiding occult studies from his superiors. Most guess it was an herbal medical book mixed with a healthy dose of astrology. But no one knows. Schaefer says the ultimate solution will require a “crib,” that is, some symbols known to relate to a specific word. He points to two hieroglyphs, assumed to be the names of Ptolemy and Cleopatra, used for cracking the writing on the Rosetta Stone.

In the case of the Voynich Manuscript, Schaefer thinks the key will be deciphering the zodiac, which is unlike the normal one in that Gemini is a man and woman, Cancer is two lobsters, and Scorpius is a lizard. Schaefer says that if anyone can crack the code of the zodiac, the solution for the Voynich Manuscript will soon follow. For a more detailed summary of the effort to decode the manuscript, Schaefer directs readers to: www.voynich.nu.

Clair Wood taught chemistry and physics for more than 10 years at Eastern Maine Technical College in Bangor.