Following Fayu's example, many Buddhist monks and nuns have used self-immolation for political purposes. Based upon analysis of Chinese historical records from the 4th to the 20th centuries, some monks did offer their bodies in periods of relative prosperity and peace, but there is a "marked coincidence" between acts of self-immolation and times of crisis, especially when secular powers were hostile towards Buddhism. For example, Daoxuan's (c. 667) "Xu Gaoseng Zhuan"(續高僧傳, or "Continued Biographies of Eminent Monks") records five monastics who self-immolated on the Zhongnan Mountains in response to the 574–577 persecution of Buddhism by Emperor Wu of Northern Zhou (known as the "Second Disaster of Wu").