I am having an indescribable amount of trouble with the passage to bridge your cut. Every time I set to work upon it, the mood forsakes me and I accomplish nothing. I am commissioning Cornelius with it now. If I should get nothing done at all, which is quite thinkable in my terribly over-driven state, it must be taken as a providential sign that you are to sing the passage entire without any cut. Be prepared for it. I make short work of it with Ander. I let him collapse after "mich sehnen und sterben" [yearning and dying] and Kurwenal follow on at once with "Mein Herr! Tristan!" [My lord! Tristan!] etc. Well, I may yet find the right way. There is still time. [...]
Best greetings to your dear wife!—If she would like to do me a great favour, will she sometime invite my niece, Clara von Kessinger (née Brockhaus), Wiesentorstrasse, No. 7, to her house? I am very fond of the child and she of me. Moreover, she is really musical, sings my songs very intelligently, and is longing to know you, so that she can hear my music in your house. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 545