According to Zhang Zhiqing, deputy director of the national library, this is the largest one-time donation the Beijing institution has received.

A special exhibition that runs through late July also kicked off at the National Museum of Classic Books, an affiliate of the NLC, on Tuesday, seeking to promote the ancient books among visitors. More than 50 copies from the new endowment are on display alongside 44 copies of ancient Chinese books from the library's original inventory, which have similar contents and thus offer comparison.

"The books donated (by Hosokawa) are quality material but with some missing parts," Lin Shitian, a researcher of ancient books at the NLC, says, adding that the variety will offer significant reference for academic studies.

The more than 4,000 books fall into 36 categories, including 25 published in China and later taken abroad and 11 printed in Japan.

Some of the books can assist Chinese academia. For example, the 50-volume Qunshu Zhiyao (Books on Governing Principles) was published in the Tang era as a collection of articles on ancient Chinese political studies. The manually copied editions got lost in China due to war after the dynasty's fall. Some editions of this precious book were brought by Japanese envoys to China. Many more editions were reprinted in Japan.

"The book was recommended for reading by Japanese emperors and other high officials in imperial court," Lin says.

"In the Edo period (1603-1868), it was not only admired by royals, but was also popular among scholars in Japan."