An Elegant Gathering of Literati on show. [Photo provided to China Daily]

In 1299, the Yuan emperor even released an edict strictly regulating the use of dragon decorations for different ranks.

The dragon with five claws was considered the highest-level, and its use was restricted to the emperor. The Ming and Qing inherited the rule.

Wang explains that a complicated ritualistic system was developed for imperial porcelain that also included color codes. For example, during the Qing Dynasty, even the royal family couldn't arbitrarily use a bowl decorated with long.

"If a bowl was both yellow inside and outside, only the emperor, the empress and the empress dowager could use it," Wang says.

"But if a yellow bowl was white inside, its ranking was lower, and the highest-ranking concubines could use it. And the status of green and purple bowls was even lower."