Yuqing inner book. The author is unknown and originated from the Tang Dynasty. The content is similar to books such as "Tongyou Jue", "Red Saw into Black Saw Jue", "Huandan Jitu Jue" and other books. "Tongzhi·Yiwenlue" contains two volumes of this book, and one volume remains today. Original source: "Orthodox Taoist Canon", Dongshen Department's Various Techniques Category.
