"It's the first time lost pre-Qin Dynasty (before 221 BC) ritual texts were found in bamboo manuscripts of the Warring States Period. They are an important reference for the study of the pre-Qin ritual system and the research into Yi Li," says Huang Dekuan, director of the Tsinghua center.

In 2008, the university received a collection of around 2,500 bamboo strips from alumni donations that are inscribed mainly with early Confucian classics and historical records.

Dating back more than 2,300 years, these manuscripts were written in the script of the Chu state.

Since 2011, the Tsinghua center has been publishing a volume of the manuscripts every year, with images of the original manuscripts, the texts transcribed in modern Chinese, meaning of words and annotations, as well as detailed information of the strips.

The work was at first led by late historian and paleographer Li Xueqin, and currently Huang.

One of the two musical texts released this year in the 13th volume, Wuyin Tu (Chart of Five Notes), is an illustration with a pentagram in the center.

Each of its projecting points is marked with one note that ancient Chinese people applied, and the extension lines on each side of the pentagram are marked with the certain note in different octaves.

The five lines of the pentagram suggest the connection between the five notes and indicate their formation, which involves ancient mathematics and conforms to classics passed down through history like Guanzi and Huainanzi (Great Words From Huainan), according to Jia Lianxiang, associate professor at the center.