Proton in Warring States refers to hostages, hostages sent to enemy countries or other countries in ancient times. Most of them are nobles or princes. Zi Chu, the father of Qin Shihuang, Qin Zhaoxiang, the great-grandfather of Qin Shihuang, and Yan Taizi Dan of the Warring States all made protons. Chu, the son of Qin Shihuang, once worked as a "proton" in Zhao, got help and finally returned to Qin.

In ancient times, "quality", when interpreted as things, was also called a basket, referring to the gifts held by people when they met each other. The etiquette of meeting each other by courtesy is called "seeing courtesy". It is an indispensable custom for aristocratic communication in the Spring and Autumn Period. In the etiquette and customs of the Zhou Dynasty, it is very important to meet each other with a reed or present a reed to the audience, and attach great importance to the gifts held by nobles of different ranks in the audience. Some poor nobles did not hesitate to use their land as collateral in exchange for jade and other items as gifts for their audience.