XIAN, China, Jan. 28 (UPI) -- The ancient tomb of tomb of Liu Qi, or Emperor Jing of Han, the fourth emperor of the Han dynasty, has revealed the world's oldest tea leaves.
The tea leaves were gathered from burial pits surrounding the tomb at the Han Yangling Mausoleum in Xian, the capital of central China's Shaanxi Province. The leaves were determined to be at least 2,100 years old -- 100 years older than an ancient Chinese document referring to the brewed beverage.
Remains of millet, rice and spinach were also discovered. Because tea plants do not naturally grow in the area of the tomb, researchers say the leaves are proof that tea was considered important enough to be deliberately buried alongside the deceased ruler.
"Our study reveals that tea was drunk by Han Dynasty emperors as early as 2,100 years BP [before present]," a team of researchers from Europe and China wrote in a new paper on the discovery -- published earlier this month in the journal Scientific Reports.
"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," study co-author Dorian Fuller, professor of archaeobotany at University College London, told NPR.
Ancient tea leaves were also recovered, several thousand miles away, from burial sites at the Gurgyam Cemetery in the Ngari district of western Tibet. Scientists dated them at 1,800 years old.
Taken together, researchers say the leaves are proof a branch of the Silk Road passed through western Tibet at the beginning of the 1st century B.C. Tea does not grow in Tibet.
"Our findings indicate that tea, as an important component of Silk Road commerce, had been introduced to the Tibetan area by 1800 years ago, during the Zhang Zhung kingdom period," researchers concluded.