Image caption The 15th Century Voynich manuscript has been described as the world's most mysterious book, which could be a complex code, an unknown language or simply a hoax

The message inside "the world's most mysterious medieval manuscript" has eluded cryptographers, mathematicians and linguists for over a century.

And for many, the so-called Voynich book is assumed to be a hoax.

But a new study, published in the journal Plos One, suggests the manuscript may, after all, hold a genuine message.

Scientists say they found linguistic patterns they believe to be meaningful words within the text.

Whether or not it really does have any meaningful information, though, is much debated by amateurs and professionals alike.

It was even investigated by a team of prominent code breakers during WWII who successfully cracked complex encrypted enemy messages, but they failed to find meaning in the text.

The book has been dated to the early 1400s, but it largely disappeared from public record until 1912 when an antique book dealer called Wilfrid Voynich bought it amongst a number of second-hand publications in Italy.

Image caption The book is 240 pages long, is written in an unknown alphabet and features mysterious pictures of unknown plants, astronomical images and naked women bathing Image caption A recent conference marked 100 years since its discovery and was held in Italy, the place it was bought by the man it is now named after - Wilfrid Voynich, an antique book dealer from Poland Image caption Inside the book there was a letter thought to be dated to 1666. It claimed the book once belonged to the Emperor Rudolf II, a member of the house of Habsburg, known to be an patron of artists and scientists Image caption Some believed that a known con artist called Edward Kelley wrote the manuscript in the mid 1500s as a hoax purely for monetary gain, but recent radiocarbon dating rules him out Image caption Many theories have appeared about the book, one of which is that it is an ancient herbal remedy book, though why some pages feature images of bathing naked ladies remains unclear Image caption Analysts have split the book into five thematic sections based on the illustrations: biological, astrological, pharmaceutical, herbal and one section on recipes previous slide next slide

Marcelo Montemurro, a theoretical physicist from the University of Manchester, UK, has spent many years analysing its linguistic patterns and says he hopes to unravel the manuscript's mystery, which he believes his new research is one step closer to doing.

"The text is unique, there are no similar works and all attempts to decode any possible message in the text have failed. It's not easy to dismiss the manuscript as simple nonsensical gibberish, as it shows a significant [linguistic] structure," he told BBC News.

100 years of analysis "There are about 25 examinations of the Voynich manuscript and most of the results show the text has similarities with natural language. This new examination is one more of this kind," says Klaus Schmeh, a cryptographer. "While we know a lot about the statistical properties of the text, we don't know enough about how to interpret them, which is one of the problems with the new research. We need to find out how different languages, encryption methods, and text types influence the statistics. "There have been numerous encrypted texts since the Middle Ages and 99.9% have been cracked. If you have a whole book, as here, it should be 'quite easy' as there is so much material for analysts to work with. That it has never been decrypted is a strong argument for the hoax theory."

Dr Montemurro and a colleague used a computerised statistical method to analyse the text, an approach that has been known to work on other languages.

They focused on patterns of how the words were arranged in order to extract meaningful content-bearing words.

"There is substantial evidence that content-bearing words tend to occur in a clustered pattern, where they are required as part of the specific information being written," he explains.

"Over long spans of texts, words leave a statistical signature about their use. When the topic shifts, other words are needed.

"The semantic networks we obtained clearly show that related words tend to share structure similarities. This also happens to a certain degree in real languages."

Dr Montemurro believes it unlikely that these features were simply "incorporated" into the text to make a hoax more realistic, as most of the required academic knowledge of these structures did not exist at the time the Voynich manuscript was created.

Though he has found a pattern, what the words mean remains a mystery. The very fact that a century of brilliant minds have analysed the work with little progress means some believe a hoax is the only likely explanation.

Unidentified language

Gordon Rugg, a mathematician from Keele University, UK, is one such academic. He has even produced his own complex code deliberately similar to "Voynichese" to show how a text can appear to have meaningful patterns, even though it is "gibberish hoax text".

He says the new findings do not rule out the hoax theory, which the researchers argue.

"The findings aren't anything new. It's been accepted for decades that the statistical properties of Voynichese are similar, but not identical, to those of real languages.

"I don't think there's much chance that the Voynich manuscript is simply an unidentified language, because there are too many features in its text that are very different from anything found in any real language."

Image caption Dr Rugg made a code purposely similar to the Voynich text to show how easy it was to produce

Gordon Rugg does not believe it contains an unknown code, which is another theory of what the text may be: "Some of the features of the manuscript's text, such as the way that it consists of separate words, are inconsistent with most methods of encoding text. Modern codes almost invariably avoid having separate words, as those would be an easy way to crack most coding systems."

As to its enduring appeal, an unsolved cipher could be "hiding almost anything", says Craig Bauer, author of Secret History: The Story of Cryptology.

"It could solve a major crime, reveal buried treasure worth millions or in the case of the Voynich manuscript, rewrite the history of science," he adds.

Dr Bauer's opinion of whether it is meaningful is often swayed, he admits. While he recently believed it to be a hoax, the new analysis has now shifted his opinion.

But despite this, he still believes it is a made up language, as opposed to a real naturally evolving one, or "it would have been broken years ago".

"However, I still feel that it's very much an open question and I may change my mind a few times before a proof is obtained one way or the other."

But Dr Montemurro is firm in his belief, and argues that the hoax hypothesis cannot possibly explain the semantic patterns he has discovered.

He is aware that his analysis leaves many questions still unanswered, such as whether it is an encoded version of a known language or whether a totally invented language.

"After this study, any new support for the hoax hypothesis should address the emergence of this sophisticated structure explicitly. So far, this has not been done.

"There must be a story behind it, which we may never know," Dr Montemurro adds.