In answering a reference question yesterday I came across the following in the February 1887 Proceedings of the Massachusetts Historical Society (p. 220). Edward J. Lowell is delivering a paper ("German Manuscript Sources for the History of the Revolutionary War") and says, in part: "The scholar who should undertake to examine the manuscripts would need a pretty good knowledge of the German language, with some familiarity with the puzzling German handwriting, knowledge of the history of the Revolution, accuracy, patience, and a strong digestion. Without the last advantage no one should venture in Germany far from the large cities."
Thankfully, he does not elaborate.