from Alma Mahler's Gustav Mahler: Memories and Letters, page 78
I met Schoenberg again later. I was acquainted with Mahler by then, although nobody knew it. I asked Schoenberg whether he was going to hear the performance of the Fourth Symphony. He answered me by one of those paradoxes he was so fond of: ‘How can Mahler do anything with the Fourth when he has already failed to do anything with the First?’ This was true ‘Schoenberg.’ Yet he was to be Mahler’s greatest and most convinced follower. Zemlinsky brought him to see us later on, and a strange sort of friendship evolved between the three of them. Zemlinsky, from an exaggeration of pride, was dry in manner with Mahler. ‘I know,’ he said. ‘Everybody wants something from him and flatters him for that reason. He shall never say that of me.’
I told Mahler this and he sent word by me that he was not to be so disingenuous but take heart and be friendly.
Schoenberg, on the other hand, was inspired by a youthful rebelliousness against his elder, whom at the same time he revered. They used to come in the evening. After one of our devastatingly simple meals, all three went to the piano and talked shop – at first in all amity. Then Schoenberg let fall a word in youthful arrogance and Mahler corrected him with a shade of condescension – and the room was in an uproar. Schoenberg delighted in paradox of the most violent description. At least we thought so then; today I should listen with different ears. Mahler replied professorially. Schoenberg leapt to his feet and vanished with a curt good night. Zemlinsky followed, shaking his head.
As soon as the door had shut behind them, Mahler said; ‘Take good care you never invite that conceited puppy to the house again.’ On the stairs Schoenberg spluttered: ‘I shall never again cross that threshold.’ But after a week or two Mahler said: ‘By the way, what’s become of those two?’ I did not, of course, say: ‘But you told me not to ask them again,’ but lost no time in sending them an invitation; and they, who had only been waiting for it, lost no time in coming. Nevertheless, it was a long time before there was much solace to be had from their intercourse together.