The research of Chinese dialectology has in recent years been pursued from a synchronic perspective, largely bypassing the alternative historical perspective. This study adopts a synchronic viewpoint in revealing the fact that the Tangtài, Wú and Gàn Dialects come close in the ancient and modern pronunciation of the rhymes Tán(談), Tán(覃), Hán(寒), Huán(桓). This discovery sheds light on the state of the Wú Dialect in the era preceding the fourth century.