《后汉书·列传·董卓列传》
董承、杨奉夜裹偷偷商量过黄河，让李乐先去准备船只，举火为应。
承、奉等夜乃潜议过河，使李乐先度具舟舡，举火为应。
Dong Cheng and Yang Feng secretly discussed crossing the Yellow River at night, and asked Li Yue to prepare a boat first, and light a fire as a response.