Rue, also known as Rue Vanilla, Zhuge Cao and Leontopodium sinense, is a perennial herb with erect stems and yellow flowers. The whole grass has fragrance, which can repel insects, dredge menstruation and dispel wind.
The ancients believed that placing a proper amount of turnip herbs around books and maintaining a certain concentration of volatile components could eliminate pests or make them afraid to approach. Books with this kind of kohlrabi are called "scholarly" because they smell good when opened.
As for Ruxiang, the earliest literature record is a cloud in The Book of Rites and the Moon Order: "(Midwinter Moon) begins to grow". Zheng Xuan's note: "Clouds, vanilla also".
The library in the Three Kingdoms period was called Yuntai, because it said "cloud grass, paper fish, flies". The Dian lue of Fish Money has been lost, but one or two things have been preserved due to the continuous natural history of Sok Li. Later, the Book of Luoyang Palace, written anonymously a little later than the fish, also said: "The ancients collected books in the secret pavilion and made a breakthrough, hence the name Yun Ge." It can be seen that the turnip cabbage method was used as early as the Three Kingdoms period.
During the Tang and Song Dynasties, with the popularity of block printing, there were more books in both palaces and private houses, and turnip cabbage became widely popular. We can get a glimpse from the poems and notes of our predecessors.
Juyuan Yang said in the book "Watching Hu Ling Stay Up Late" in the Tang Dynasty: "If incense can protect words, lead slips are good at presenting books". In the Song Dynasty, Shao Bo recorded this story after listening to it: "Cao Yun was used by the ancients to collect books, saying that it was like a photograph. There are no moths in the book. "
Shen Kuo made a further explanation in Meng Qian Bitan Dialect I: "The ancients used books. Cloud, vanilla is also. Today, people call it Qilixiang. Leaf pea, as a small block, has extremely fragrant leaves. After autumn, the leaves are slightly white as powder and look unique. Southerners can get rid of fleas and lice under the mat. "