Photo: Screenshot from online

A set of ancient Chinese wooden slips, also known as mudu, has been recently discovered in Southwest China's Chongqing Municipality. 

Featuring characters related to the ancient Chinese astronomical calendar, the wooden slips are the first ever discovered in the country to reveal celestial secrets. 

The set includes a total of 23 single wooden slips. Wooden slips like these, along with Chinese bamboo slips, or jiandu, were the "earliest Chinese documents featuring words," archaeologist Wang Meng told the Global Times, adding that such an invention was also the "most important form of early Chinese books." 

On each "page," archaeologists were able to find characters written in ink relating to the Chinese Tiangan Dizhi, or the "Ten Heavenly Stems and 12 Earthly Branches, an ancient astronomical calendar system involving 10 Chinese characters used as ordinals and another 12 characters used to divide a day into 12 two-hour periods. For example, wu (lit: noon) refers to the time from 11 am to 1 pm. 

This wood slip calendar, which is still in a "perfectly good condition," was discovered in a Western Han Dynasty (206BC-AD25) tomb, according to Huang Wei, an associate researcher at the Chongqing Institute of Cultural Relics and Archaeology. 

"We speculate that all those individual slips were all bound together. We still have not yet verified the exact purpose of the relic and why it was used as a burial object," Wang noted. 

Despite its purpose being unknown, Sichuan archaeologist Yu Pei'er explained to the Global Times that the discovery might be closely "connected to the tomb owner's profession and beliefs."

"Wooden and bamboo slips are often found in ancient Chinese tombs, but the astronomical contents of the findings inspire us researchers to further investigate the specific burial customs of the area," Yu remarked. 

The wooden slips were discovered in the Guankou No.1 Western Han Tomb located in the Wulong district of Chongqing. According to the information inscribed on the slips, the tomb dates back to 193BC, making it one of the oldest Western Han Dynasty tombs ever discovered. 

"This is the first time we've found a tomb with a clear dating that puts it during the Western Han period in China," Wang said, adding that the tomb is also the best preserved wooden-chambered tomb ever found in Southwest China. 

Including the wooden slips, a total of 600 artifacts, including lacquerware, wood and bamboo wares and bronze wares were unearthed from the tomb. Ancient accessories such as earrings and plates made of lacquer are some of highlight discoveries due to their incredibly well-preserved condition.