《明史·列传·卷五十九》
又采用谋士的话，沿着边防要塞的边缘，隐藏埋铁椎深三尺，马蹄一踏上就会穿透。
又用策士言，缘边要害，隐铁椎三尺，马蹄践辄穿。
By another advisor’s suggestion, along the edge of the border garrison, iron spikes three feet deep were hidden and buried so that any horse that stepped on them would be pierced through.