From the Bencao Gangmu‧Sequence. The medicinal properties of sour and salty tastes are inward and downward, without the tendency to "ascend"; the medicinal properties of sweet and pungent tastes are outward and dispersing, without the tendency to "descend". However, this is not absolute. For example, cultivated purple perilla fruit is pungent and warm, and Aquilaria is pungent and slightly warm. In terms of their nature and flavor, both should ascend, but due to their heavy quality, they actually descend.