When was Zhi Yong's cursive script Preface to Lanting Collection discovered?

Sui dynasty. Preface to Lanting occupies a supreme position in the history of calligraphy in China, and is known as "the best running script in the world". After writing the book, Wang Xizhi was collected by Zhiyong. Zhi Yong studied the Preface to the Lanting Pavilion in yunmen temple for 30 years, and he was able to "solve his own family style". In Su Dongpo's view, Zhiyong was the only one who got the "Two Kings" pen.