According to Li Guojie, every piece of Yong Zi should be perfectly round, flawless and without bubbles. The white chessmen should be as bright as egg white, the dark ones as green as jade.

The method of making Yong Zi was partly lost during wartime in the middle of the 19th century. As a result, its production was stopped for over a century.

In 1964, then vice premier Chen Yi, who was a fan of Weiqi, visited Yunnan and asked local governments to recover this legacy and restart its production.

With the help of local authorities, Li's family spent over 20 years in search of the lost method and started production of Yong Zi again. Now it is listed in Yunnan's intangible cultural heritage.

According to Tao Xiaochang, head of Baoshan Yong Zi Intangible Cultural Heritage Museum, traditional Yong Zi production includes ten procedures. Some of them, such as smashing and grinding, are now carried out by machines instead of by man.

"The name of Yongchang has changed into Baoshan. But Yong Zi is always the symbol of our culture," says Tao.

Now Li Guojie, the 11th generation down from the inventor, has resumed this art, as Yong Zi is now used in many games.