[...] The fine impression I gained of you recently through your performance as Senta in The Flying Dutchman has grown upon me, so that I must tell you of my wish to see you take part in some of next year's performances of my Parsifal. The excellence of the tenor, Gudehus, has already decided me to recommend that you two should sing in Tristan and Isolde in Dresden; I can be sure that the other rôles will be equally well cast. I should also be very well satisfied if you would give Isolde in London, where I know you have an engagement. It is understood that in expressing my wishes to you my other relations with the general management of the Dresden Court Theatre are not in any way affected. In making over Tristan and Isolde, I attach no other conditions than those which the general management's sense of what is fit will be inclined to accept. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 727