《资治通鉴·隋纪·隋纪二》
突利可汗望见四处烽火同时燃起，向长孙晟询问情况，长孙晟欺骗他说： 烽火台都是建在高处，所以能看得很远，必定是发现有敌军入侵。
突利见四烽俱发，以问晟，晟绐之曰： 城高地迥，必遥见贼来。
When Tujili Khan saw beacons fired everywhere concurrently, he inquired about the situation from Zhangsun Sheng. Zhangsun Sheng deceived him, saying: “Beacon towers are all built on high ground which enables one to see far and wide, so they must have spotted an invading enemy.” 