Archaeologists exploring a nearly 2,200-year-old Chinese tomb belonging to an emperor of the Han Dynasty recently stumbled on a treasure: the oldest tea ever found. This new find not only provides new evidence that ancient Chinese royalty drank tea, but could reveal new details about the history of the Silk Road.

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The ancient tea was discovered in the Han Yang Lin Mausoleum, a tomb built for the ancient Han emperor Jing Di near the modern-day city of Xi’an in western China. When the tomb was excavated during the 1990’s, archaeologists discovered many treasures, including pottery figures, weapons, and even several chariots complete with horses.

Alongside these relics, the researchers also discovered a mass of partially-decomposed plants. Some of these 2,150-year-old remains were preserved so well that researchers could identify grains like millet and rice. But it took a team of scientists armed with specialized equipment decades to realize that this mysterious brick of plant matter was actually ancient tea, Sarah Laskow reports for Atlas Obscura.

“The discovery shows how modern science can reveal important previously unknown details about ancient Chinese culture,” Dorian Fuller, Director of the International Center for Chinese Heritage and Archaeology in London, who was not involved in the study, tells David Keys for the Independent. “The identification of the tea found in the emperor’s tomb complex gives us a rare glimpse into very ancient traditions which shed light on the origins of one of the world’s favorite beverages.”

In the study, published in Nature’s open access journal, Scientific Reports, the researchers note that although the first unambiguous written reference to tea dates back to 59 B.C., the exact origins of one of the world’s most popular beverages is still a mystery.

It’s popularity among the western Uighur people and northern Chinese is generally attributed to the Tang Dynasty that ruled during the 7th and 8th centuries A.D., and the previous oldest sample of tea remains dates back to about 1,000 years ago.

The researchers identified the remains as tea leaves by examining the tiny crystals on their surface, according to the study. This showed that the tea was likely a particularly fine one made from young, unopened tea buds and dates back to around 141 B.C., when Emperor Jing Di died and was sealed in his tomb.

This discovery not only indicates that Jing Di was a big tea drinker, but suggests that tea was already being exported to Tibet along trade routes that may have helped blaze the trail for the Silk Road, which starts in Xi’an, Laskow reports. But while these details help paint a clearer picture of how tea became so popular, for now, its origins are still shrouded in mystery.