What is the earliest extant collection of Guqin music in China?

The Magic Secret Music is a collection of ancient piano music compiled by Zhu Quan, the son of Ming Taizu. It was written in Hongxi Yisi in the early Ming Dynasty (A.D. 1425), and it is the earliest collection of piano music in China. The 64 piano pieces included in the book were selected by the editor from "thousands of piano pieces edited by several musicians" at that time, some of which were quite influential in history.