Nagatsumi - Eizumi

...This is the amount of tax collected in the late Middle Ages, calculated based on the Yongle coin (Yongle Tongbao), a phenomenon unique to the Kanto region. It is also called Eizumi, Eimori, and Eiwake. The practice of paying tax in coins began at the end of the Kamakura period, when the kanko system was established, in which feudal lords indicated the number of bunsen (amount of land) of their fiefs. As the use of Yongle coins spread, they came to be the standard among various types of coins in the eastern part of the country, and the later Hojo clan limited their tax payments to Yongle coins, calling the bunsen tax paid in Yongle coins Eikyo, and this practice spread widely throughout the Kanto region....

*Some of the terminology explanations that mention "naigatsumi" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…中世後期に永楽銭(永楽通宝)を基準として算定した年貢収納高で，関東特有の現象である。永積，永盛，永別などの呼称もある。年貢銭納は鎌倉末期に始まり，領主が知行地を分銭何貫文の地と表示する貫高制が成立したが，永楽銭の通用がひろまるにつれて東国ではそれが諸種の銭貨の中で基準たる地位をしめるにいたり，後北条氏が年貢銭納を永楽銭に限定し，永楽銭による分銭高を永高と称し，その慣習がひろく関東一円にひろまった。…

※「永積」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報