[...] From your brief intimations I take it that our old friend Nietzsche has been holding aloof from you also. There is no doubt that very striking changes have taken place in him. But those who used to observe him years ago in his mental fits can only tell themselves that a certain catastrophe, long dreaded, has now set in, not altogether unexpectedly. I have preserved enough friendship for him not to read his book (after glancing through the pages as I cut them) and I can only wish and hope that some day he will thank me for this. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 711