Xu Si 許汜

When Lü Bu left Yuan Shao to follow Zhang Yang, he called on Zhang Miao on the way and, on parting, they clasped hands and swore an oath together; Yuan Shao heard of this and bore a deep grudge, and Zhang Miao was uneasy. In the 1st year of Xingping (194), when Taizu went to campaign against Tao Qian again, Zhang Miao's younger brother Zhang Chao plotted to rise against Taizu together with Taizu's general Chen Gong and the Attendant Gentlemen Xu Si and Wang Kai. Records, Wei 7 §12

Chen Gong persuaded Zhang Miao that since the province's army had gone east and left it empty, they should take in Lü Bu and govern Yan Province together, and Zhang Miao followed his advice. Chen Gong led his troops to welcome Lü Bu, made him Governor of Yan Province and occupied Puyang; the commanderies and counties all responded, and only Juancheng, Dong'a and Fan held out for Taizu. Chen Shou's main text does not separately record what Xu Si did in this affair. Records, Wei 7 §12–13

The account of Chen Deng in the Biographies of Lü Bu, Zhang Miao and Zang Hong states that Chen Deng, courtesy name Yuanlong, won an awe-inspiring name at Guangling and died at thirty-nine, and then continues with this episode. Later, Xu Si was in the company of Liu Biao, Governor of Jing Province, together with Liu Bei. When Liu Biao and Liu Bei were discussing the notable men of the realm, Xu Si said, 'Chen Yuanlong is a man of the lakes and seas who has never shed his arrogant spirit.' When Liu Bei asked whether Master Xu's judgment was right, Liu Biao answered that if he said it was wrong, this man was a fine gentleman who would not speak idly, and if he said it was right, Yuanlong's name carried great weight throughout the realm. Records, Wei 7 §31

When Liu Bei asked what had happened, Xu Si said that in the past, during the disorders, he had passed through Xiapi and met Yuanlong, who showed none of a host's regard for a guest, did not speak with him for a long time, and himself climbed onto the large bed to sleep while making his guest sleep on the lower bed. Liu Bei said that since Xu Si bore the name of a gentleman of the state, Yuanlong would have hoped he would worry for the state and forget his own household, but he had sought fields and inquired about houses and said nothing worth taking up, which was what Yuanlong disdained; had it been Liu Bei himself, he would have slept on top of a hundred-foot tower and made Xu Si sleep on the ground. Liu Biao laughed heartily, and Liu Bei said that Yuanlong's civil and martial ability, courage and resolve could be found only among the men of old. These two passages are the only places in Chen Shou's main text where Xu Si appears. Records, Wei 7 §32–33