They say never judge a book by its cover - but sometimes you can't even trust the words written on the pages.

This week, scientists in California are busy investigating an archaic hymn book of religious text dating back to the 11th century. In ordinary circumstances, this weathered volume would be a priceless historical artefact in its own right. But these are not ordinary circumstances.

This time around, the religious script is a smokescreen: an ancient cover-up concealing a far older truth – one that dates back many more centuries into the past, to a man considered one of the fathers of the medical science we have today.

That man was Galen of Pergamon, a Greek physician and philosopher born under the Roman Empire during the 2nd century, who through his teachings and writings became known as one of the greatest medical minds of antiquity.

But not all those communications were carefully tended by history.

(Farrin Abbott/SLAC)

The parchment being examined by scientists this week at the Department of Energy's SLAC National Accelerator Laboratory was originally inscribed with the teachings of Galen, translated by an unknown hand centuries after the physician's death, before being hidden by psalms for an entire millennium.

Before the cover-up, Galen's medical treatise was written down in ancient Syriac during the 6th century, most likely by someone at St. Catherine's Monastery in Egypt, researchers think.

Then, around 500 years later, this important ink was scraped off the pages and overwritten with religious psalms – almost certainly for economical reasons (parchment wasn't cheap) and not because there was a malicious agenda to conceal Galen's work.

For nearly a decade, scientists and scholars have been using multispectral imaging to try to reveal the scrubbed traces of the ancient underlying text, and thanks to a team at SLAC's Stanford Synchrotron Radiation Lightsource, we might finally succeed in deciphering the hidden words this week.

The researchers are using high-energy X-rays generated by a cyclic particle accelerator to expose infinitesimal residues of ink left buried in the parchment from the original inscriptions – giving researchers an unprecedented glimpse at some of the foundations of medical knowledge as they existed almost 2,000 years ago.

(University of Manchester/SLAC National Accelerator Laboratory)

In the image above, the vertically oriented characters are the religious text of the 11th century, while the fainter horizontal Syriac is Galen's translation hidden underneath.

Previous efforts have sought to use ultraviolet, visible, and infrared wavelengths to penetrate the lost writings – but much like the ominous inscription concealed in Tolkien's One Ring, sometimes it takes a more extreme trick to reveal words intended to be hidden.

"The first initial results are incredibly mind-blowing," classicist Peter Pormann from the University of Manchester in the UK told Newsweek.

"This is a unique witness to this particular text."

The new imaging effort, which takes 10 hours to analyse each of the 26 pages selected from the volume, has already revealed sections of the text not seen by anybody in a thousand years, including a previously unreadable preface.

(Andy Freeberg/SLAC)

If they're successful, it will open a new chapter in our understanding of one of medicine's earliest visionaries – and with another 200 pages of hidden inscriptions still remaining, who knows what scraped secrets we'll discover?

"Galen is the most important and most influential physician arguably of all time," Pormann told Newsweek.

"This is basically our history, this is how medicine developed."