《宋史·列传·卷一百七十七》
京城也有未署名的书信，说某日火烧蓑城苇，率领两侧翼的士兵作乱，丞相就没有忧虑了。
京城亦有匿名书，言某日烧蓑城苇，率两翼兵为乱，丞相可无忧者。
There was also an anonymous message in the capital, saying that if the reeds of蓑城were burnt on a certain day, soldiers on both flanks would rebel and the prime minister would have nothing to worry about.