《北史·列传·卷四十六》
他秘密对宇文椿说： 用兵，要有诡诈之道。你现在建造军营，不需要用幕布搭帐篷，可砍伐柏树搭起棚庵，表示正住在这地方。
宪密谓椿曰： 捕者诡道，汝今为营，不须张幕，可伐柏为庵，示有处所。
He told Yuwentun secretly: If you use troops, you must have a treacherous approach. Now that you are building military camps, you don't need to use curtains to set up tents. You can cut down cypress trees to set up shelters, indicating that you are living in this place.