雷池

Today only survives in the set phrase 不敢越雷池一步 'dare not cross Lei Pond by a step', from a 4th-century letter by Eastern Jin statesman Yu Liang (庾亮) to general Wen Qiao (温峤) in 《晋书·庾亮传》, telling him to stay south of Lei Pond and not march on the capital.

culture

Geographically, 雷池 was a real lake in present-day Wangjiang County (望江县), Anhui Province. As a place name it is now obscure - the figurative meaning has eclipsed the literal one in everyday usage.