Classes about the Manchu language and the ethnic group's customs have been given to students at a primary school in the Kuancheng Manchu autonomous county, Hebei province, once a week since December 2013. Of the county's population, 64 percent are Manchu people. Xinhua

Archaic language is helping historians to solve Qing mysteries, as Zhao Xu reports.

A bereaved emperor who condemned his son to a life of confinement, a bright prince entangled in a deadly political struggle, and a long-gone royal mansion that stood witness to all the love, hate and sadness - Yan Chongnian would have had no chance to uncover this distant past if he did not "hold the key".

"That key was my knowledge of the Manchu language," the historian said, referring to the language used by the rulers of China's last feudal dynasty, the Qing dynasty (1644-1911).

Although viewed by many as the ultimate authority on all issues related to that period, he experienced a moment of uncertainty a few years ago when he was invited to the site of what was once a grand abode for a Manchu wangye, or duke, in a northwestern suburb of Bejing.

"Judging by what remained of the construction - the groundwork and the moat - it was worthy of a wangye," Yan said. "But here lies an apparent contradiction: During the Qing dynasty, wangye lived in the center of the capital, inside what is now modern Beijing's second ring road."

According to Yan, this contradiction had led some researchers to believe the compound, now barely discernible, had belonged to Wu Sangui, a Han general who allied with the Qing at the empire's founding and was made a duke. Yan was unconvinced.

"Not long after that visit, I accepted an invitation to teach at a university in Taiwan," he said. "During that stay in 2008, I spent 10 days searching for information at Taipei's Palace Museum, which is filled with invaluable antiques and documents originally from its counterpart, the Palace Museum in Beijing.

"There, I tripped over a file compiled by the Qing ministry of internal affairs on the completion in 1721 of a royal abode, at the same location as the one I saw in Beijing."

Yan couldn't wait for the end of his semester to fly back to Beijing. "I'd had the story's ending," he said. "What I needed next was the opening."

That was soon found in the countless Qing files kept by the First Historical Archives of China, in Beijing.

"A construction of that scale usually took two to three years to build, so I jumped back to three years before the building's completion and started my search. There, also among the internal ministry's documents, was a file that echoed the one I found in Taipei, not only in content but also the paper and binding. This one was on the commencement of construction, in 1718.

"It was built by Emperor Kangxi (1654-1722), arguably the greatest Qing emperor, for his seventh son, Yinreng. Both files were written in the Manchu language," he said. "I would never have uncovered that history if I hadn't known the archaic language."

Indeed, archaic is the word mostly associated with a language once used by the rulers of the Middle Kingdom, as China was then known.