《明史·列传·卷二百一十五》
燕王从古北口出发，侦察了解到乃儿不花在迤都扎营，于是冒着大雪急速进兵，离敌只有一碛远，敌人并不知晓。
燕王出古北口，侦知乃儿不花营迤都，冒大雪驰进，去敌一碛，敌不知也。
King Yan set out from Gubeikou, was informed by scouts that Naier Bugha had made camp in Yidu, and so, pressing forward through heavy snow, reached a distance of only a single ridge from the enemy without the latter's knowledge.