Dadao Tongxuan Yao: Lost Tang Daoist Encyclopedia

The compiler of The Essentials of the Great Dao’s Profound Mystery (Dadao Tongxuan Yao) is unidentified.

It was probably compiled during the Kaiyuan reign period (713–741) of Emperor Xuanzong of the Tang Dynasty. The original work consisted of approximately 30 volumes, divided into 81 sections (pin), and was another large-scale Taoist encyclopedia following the Wushang Miyao (The Supreme Secret Essentials) of the Northern Zhou Dynasty.

This text was not included in the Zhengtong Daozang (the Official Taoist Canon of the Ming Dynasty).

According to the records in Ōfuchi Ninji’s Dunhuang Daojing Mulu Bian (A Catalogue of Dunhuang Daoist Scriptures), there are seven manuscript copies of this work among the Dunhuang manuscripts, detailed as follows:

Manuscript P2456 (covering Volume 1 and Volume 6): It is composed of two pasted-together parts. The latter part is Volume 1, with 133 surviving lines; the former part is Volume 6, with 161 surviving lines.
Manuscript P2466 (covering Volume 5): 110 lines remain.
Two manuscripts covering Volume 7 (S3681 and "Di Zi 17"): Both are intact from the beginning to the end, with 206 lines preserved.
Manuscript P2363 (covering Volume 12): 49 lines remain.
Two manuscripts covering Volume 14 (the copy collected in Zhensong Tang and Manuscript P3839): Both are fragmentary, with a total of 204 lines preserved.

The seven manuscripts mentioned above preserve approximately 6 volumes and 27 sections of the original work.

The text excerpts from Taoist classics of the Northern and Southern Dynasties, Sui, and Tang dynasties, and compiles them by category. All quoted Taoist texts are clearly marked with their sources, and a total of 56 texts are cited—including some ancient Taoist scriptures that have since been lost.

Ōfuchi Ninji conducted a detailed textual research on this work.