The papyrus is one of a number in the hands of experts at the University of Basel. The Swiss collection has included the mysterious papyrus since the 16th Century.

The mystery came from what appeared to be mirror writing, found on both sides. The both-sides presentation was just one way in which the mysterious document was different.

Most intact papyri are mundane documents, such as contracts and receipts, or letters from one person to another. The newly decoded papyrus contains a literary text, the Swiss researchers said.

Using infrared and ultraviolet technology, the University of Basel team discovered that the papyrus was, in fact, several layers glued together. The team employed a restoration specialist to separate the sheets. Once the sheets were separate, experts were able to read what was written on them.

The link to Galen, one of the most famous names in Greek scientific history, comes from the deciphered content, which is medical in nature and describes a condition known as "hysterical apnea." The researchers compared the newly decoded text to that found in other similar papyri, held by the Archdiocese of Ravenna in Italy, known to be written by Galen. Some of those contained multiple pieces of writing, in the form of medieval "recycling": In those days, it was quite common to reuse papyrus or parchment or whatever writing material was to hand because it was either scarce or labor-intensive to produce. Such a manuscript was known as a palimpsest.

Galen is thought to have coined the term "hysteria" and is known to have written on the condition. If Galen himself didn't write the text, then it was a commentary on his work, the researchers said.

The researchers also suggested that the glued-together sheets of papyrus themselves could have been used as a book binding.