First, the usage of "letter":
1, the "letter" of "envelope" is a noun as an adverbial, which means it is packed in a box. From "Jing Ke Stabbed the King of Qin", the prince heard it, rushed to it, and wept bitterly. In desperation, I accepted Fan's first letter and sealed it.
When the prince heard about it, he rushed to the carriage, fell on Fan's body, and began to cry, very sad. Water under the bridge. There is no way to save it, so I packed Van Yuqi's bag and put it in a box.
Second, the source:
1 "Jing Ke Stabbed the King of Qin" comes from "The Warring States Policy Yance III", which describes the tragic historical story of Jing Ke stabbing the King of Qin during the Warring States Period, reflects the social and political situation at that time, and shows Jing Ke's spirit of valuing righteousness over profit and bravely sacrificing for Yan. Through a series of plots, dialogues, actions, expressions and demeanor, the article expresses the character and shapes the image of the protagonist Jing Ke.
2. In 227 BC, Jing Ke came to Qin to assassinate Ying Zheng, the king of Qin, with the maps of Yan Du Kang and Fan. Before he left, Yan Taizi Dan and others saw Jing Ke off at the Yishui River. The scene is very tragic. A friend hit Zhu with a gift, and Jing Ke sang to the beat, "The wind is rustling and the water is cold, and the strong man is gone forever." This is a poem sung by Jing Ke when he said goodbye. When Jing Ke presented a map of Yan Du Kang, the attempt to assassinate him failed.