[...] Let me just merely hint to you the troubles these concerts have brought on me, since I had no such reliable friend as you by my side at the time—how the practical difficulties and disappointments (which had to be carefully concealed from people in general) exceeded all calculation. Let me tell you further, that one main object of these concerts—namely, to induce a certain man to guarantee my German operatic enterprise—has not been attained, and that I am on the point of cancelling this undertaking, important as it is for my support in the immediate future (it was to have made possible for me the first performance of Tristan). I think of writing to put off my German singers, who had accepted with enthusiasm, thereby leaving the very kernel of my intentions unfulfilled for God knows how long. Then think to yourself whether the enthusiastic acclamations of the Parisian public could give me any joy. As I say, I am going straight to the point of getting my Tannhäuser accepted by the Grand Opera. Fould, absolute monarch of the Grand Opera and Meyerbeer's intimate friend, eludes me; I must try to get at him through the Emperor himself—whose procurer he is, by the way. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 456