the number four; complex form used for financial purposes is 肆 sì

imperial or royal court; government; a dynasty or the reign of a particular ruler

A collection of biographies of famous Buddhist monks from the Eastern Han to the early Liang Dynasty, compiled by Huijiao in the 6th century. It is the first of the four major biographical works of its kind, together known as the 四朝高僧传 sì​cháo​gāo​sēng​zhuàn.