In the popular imagination, the Rosetta Stone alone decoded hieroglyphics, cracking open the ancient Egyptian universe. In fact, it was one of several stone inscriptions that proved pivotal in the painstaking scholarly task of deciphering Egypt’s oldest form of writing. Another was the Decree of Canopus, the first version of which was discovered in 1866 at Tanis, a one-time dynastic capital located in the northeastern Nile Delta.

Measuring nearly seven and a half feet in height, it was inscribed with three languages: Egyptian hieroglyphs, a cursive script known as demotic, and Greek. The inscription records the great assembly of priests that gathered in Canopus in 238 B.C.E. during the reign of Ptolemy III. With a greater number of different hieroglyphs than the Rosetta Stone, it played a crucial role in 19th-century research and today is a centerpiece of the Egyptian Museum in Cairo’s collection.

Bust of Ptolemy III. Photo: courtesy Getty Villa.

On September 9, the Ministry of Tourism and Antiquities announced that another version of the Decree of Canopus had been found at an archaeological site known as “Hill of the Pharaohs” in El Husseiniya, a city north of Cairo.

“The significance of this discovery lies in the fact that it is a completely new version of the Canopus Decree,” the Ministry said in a statement. Researchers are now expected to pick through the stela and compare it to other versions.

Unlike the previous six copies of the decree that have been found over the past 150 years, this version is inscribed solely with hieroglyphics. The four-foot sandstone slab is in excellent condition and, though not as elaborate as the Egyptian Museum’s version, is carved with a winged sun disk flanked by two royal cobras on the top.

Below this, there is a blank space. Stefan Pfeiffer, an Egyptologist who has written on the Canopus Decree, believes this shows the stele is incomplete. “Different stela had depictions that were adapted to local religious backgrounds, we can’t be sure what it would have looked like,” Pfeiffer said over email, noting that there is also enough blank space below the Hieroglyphic text for demotic.

The Canopus Decree found in 1881 at the Egyptian Museum in Egypt. Photo: Amir Makar/AFP via Getty Images.

Beyond its use as a translation tool, the Decree of Canopus has helped scholars understand Ptolemaic Rule in Egypt. The decree, which the entire Egyptian priesthood ordered be inscribed on steles and disseminated throughout the territory’s temples, touches on an exceedingly wide range of subjects.

It records Ptolemy III’s military expedition into Asia to recover divine images as well as the pharaoh’s suppression of domestic insurgencies. It notes the ruler’s wisdom and benevolence in importing grain during a recent drought. It declares Ptolemy III and Queen Berenice’s recently deceased daughter, princess Berenike, a goddess and proscribes the cultic activities that should take place to honor her.

It also issues the most accurate solar calendar to date in the ancient world, adding in an extra day every four years. “May it be known to all men that the arrangement of the seasons of the year was somewhat defective,” the Decree of Canopus states. “The rules which exist as the laws of science and the ways of heaven have now been set right.”

Today, the city of Canopus where Ptolemy III and his priests convened 2,200 years ago lies sunken city off the coast of Alexandria, the victim of earthquakes and rising sea levels. Earlier this year, for the first time in a quarter century, Egyptian archaeologists begun conducting underwater excavations.