《资治通鉴·汉纪·汉纪二十四》
天象复杂，难以向陛下述说清楚，我虽呈献上天文图表，但仍需口说解释，然后才能使陛下明白，请陛下赐一点清闲的时间，让我指着图表向陛下详述。 
天文难以相晓，臣虽图上，犹须口说，然后可知；愿赐清燕之闲，指图陈状。 
Celestial phenomena are complicated, and it's hard to express myself clearly to Your Majesty. Though I've offered the celestial charts, I still need verbal explanation to make Your Majesty understand. I hope Your Majesty can spare some time and I'll explain the charts to Your Majesty in detail.