A drop of glowing liquid drips from the tip of an iron stick, freezes into a perfect hemisphere after resting on a long and cold iron plate.

That's one of the steps how Li Guojie from Baoshan, once called Yongchang, in Southwest China's Yunnan province, makes Yong Zi, a type of Weiqi chessmen. Just like his ancestors did over 400 years ago.

Standing beside a stove over 1,000 degrees Centigrade, Li puts one end of the iron stick into the heated liquid, a melted mixture of agate, topaz, jadeite and amber found in Baoshan, until it is coated by a thick layer of lava. Then he pulls out the stick, repeats the drip-drop move above the plate, and lets gravity do the rest.

The 25-year-old makes seven to nine chessmen every time. He and his partners make about 1,000 Yong Zi during an eight-hour shift.

Yong Zi, literally meaning of "chessmen made in Yongchang", is considered best for Weiqi, a popular board game for two players which originated in China over 2,500 years ago.

In Li's view, Yong Zi is a combination of craftsmanship and artistic beauty. "The step of drip-drop is most difficult. You don't have a mould, all you have is your hand and experience," he says.

The same experience has run through Li's family line for over 400 years. In 1512, Li Dezhang invented Yong Zi, whose unparalleled quality since then has won fame across the country.

In Xu Xiake's Travels, Xu, a famous adventurer and geographer in the late Ming Dynasty, said, "The chessmen made in Yongchang, Yunnan province, are the best of its kind."