《明史·志·卷五》
隆庆二年三月戊午日，延绥堡整城角旗杆发出火光，灼灼有声响。
隆庆二年三月戊午，延绥保宁堡城角旗杆出火，灼灼有声。
On Wuwu day in the third month of the second year of the Longqing era, a firelight appeared from the flagpole at the corner of Yansui Fort, blazing and with a crackling sound.