Most people thought the Dutch scholar-diplomatic Van Gulik 高羅佩 was the first European who discovered Donggao Xinyue 東皋心越 . He published two related works in 1940s. However, I came across an article dated to 1896 by Ernest W. Clement I1860-1941) who already introduced both Zhu Shunshui 朱舜水 and Donggao in Mito. No Chinese scholars would have known Zhu Shunshui and Donggao without the efforts of these two European scholars.
The full reference of the article is:
Journal/Book Title: Transactions of the Asiatic Society of Japan.
Article Title: Chinese refugees of the seventeenth century in Mito.
Article Author: Clement, Ernest
Reference to van Gulik's works:
明末義僧東臯禪師集刊 / Ming mo yi seng Donggao chan shi ji kan
商務印書館 : 民國 33  Chongqing : Shang wu yin shu guan, Minguo 33 , , 152 p.
Chan master Donggao. Chinese. With added preface in English.
The Ch'an master Tung-Kao : a loyal monk of the end of the Ming period
by R. H. van Gulik.
Chungking, China : Commercial Press, 1944. 1 v. (unpaged) : ill.