In 1966, a Mexican City-based antiquities collector named Dr. Josué Sáenz received a phone call that would both change his life and stir up a whirlwind of controversy for decades to come. The man on the other end of the line promised Sáenz something fantastical if he would board a plane to the city of Villahermosa and agree to travel with locals there to a remote location. Intrigued, the collector later found himself in the foothills of the Sierra de Chiapas mountains, surrounded by villagers who had years earlier discovered a number of ancient artifacts in an undisclosed cave.

One of the items, a manuscript of 11 pages, was particularly intriguing. Made of fig bark sheets, it contained weather-stained, torn illustrations of what appeared to be Maya origin. If real, its value would be priceless. Only three other Maya manuscripts, or codexes, had ever been discovered –– all of them shipped back to Europe during the 16th century.

According to one account, Sáenz wanted to have the items independently verified before making a purchase, but the villagers balked. They gave him 20 minutes to decide to pay $30,000 for the lot or walk away forever. Sáenz eventually agreed, and returned to Mexico City anxious to make sure he had made the right choice.

Grolier Codex The 11 water-damaged pages of the Grolier Codex have been declared the oldest surviving manuscript of the ancient Americas. (Photo: Justin Kerr)

In time, all of the artifacts Sáenz brought home with him that day, including an elaborate mask and a ceremonial dagger, would be accepted as authentic except one: the manuscript. While radio carbon dating traced the fig paper back to the 13th century, the markings sketched on top were dismissed as forgeries.

“It is possible that it is a late colonial period codex, but more likely it was painted as recently as the 1960s when looters realized the blank paper they found in a cave would be much more valuable with painted designs,” wrote Florida Museum of Natural History’s Susan Milbrath in a 2002 paper.

Eventually called the Grolier Codex — so-named for the Grolier Club in New York City where it was briefly displayed in the 1970s — the document remained disputed until earlier this year when researchers decided to take a closer look.

“It became a kind of dogma that this was a fake,” Brown University professor Stephen Houston, who led the study team, said in a statement. “We decided to return and look at it very carefully, to check criticisms one at a time. Now we are issuing a definitive facsimile of the book. There can’t be the slightest doubt that the Grolier is genuine.”

Grolier Codex Two pages from the Grolier Codex. Note the blue color in the right page, a pigment unique to cultures of the ancient Maya and Aztec. (Photo: Justin Kerr)

In a paper published in the latest issue of the journal Maya Archaeology, the researchers outline how they verified the Grolier's ancient origins. One of the biggest clues was the Maya blue pigments used in the sketches of the figures. The formula for this unique bright azure blue, created by cultures such as the Maya and Aztec, was lost for hundreds of years. Only recently have scientists cracked how these ancient civilizations might have created the resilient color, according to LiveScience.

In addition, the researchers also discovered that some of the deities represented in the codex had not been discovered in 1964. For forgers to create these and the Maya blue would have required pure guesswork and a whole lot of luck.

As for why the Grolier was hidden away in a cave, Houston says its value as a "sacred work" likely made it and other ancient documents a target of Spanish inquisitors.

The team is hopeful that despite the manuscripts's colorful discovery, its authenticity will no longer be disputed.

“A reasoned weighing of evidence leaves only one possible conclusion: four intact Mayan codices survive from the Precolumbian period, and one of them,” the team concluded in the paper, “is the Grolier.”