Klindworth has just been playing me your great Sonata. We spent the day alone together; he dined with me and afterwards I made him play. Dearest Franz, you were indeed at my side. The Sonata is beautiful beyond belief, great, lovable, deep, noble, sublime as you are yourself. I have been most profoundly affected by it and all this London wretchedness was suddenly forgotten. I can say nothing more to you just now, immediately after the performance, but I am as full of what I have said to you as a man may be. Once more you were with me. Oh, could you actually be so in the flesh and soon! Only so we could live beautifully!! Klindworth has amazed me by his playing; no lesser man than he could venture to play a work of yours to me for the first time. He is worthy of you indeed, indeed!
Richard Wagner
Source: Letters of Richard Wagner, Volume 1, ed. Altmann/Hull (London: Dent, 1927), No. 276