I N T R O D U C T I O N T O V O L U M E 1 3 l x x i Nobel Prize moneys envisaged in the divorce agreement had finally arrived, Ein- stein urged his Swiss family to purchase a house in Zurich, which they did in May 1924, using a significant portion of the prize money (Doc. 400). During his brief sojourn in Zurich at the end of his trip overseas, Einstein also instructed Albert Karr-Krüsi, the manager of his Swiss finances, that stock shares (possibly of the Auergesellschaft) be given to Elsa Einstein and her daughters in the case of his death (Doc. 446). In a period of economic instability and unfavorable exchange rates between the German mark and stronger European currencies, Einstein avoided transferring to Germany the income he had earned abroad. He could thus avoid both loss in the relative value of the money and taxation by the German authorities. He arranged for his Dutch salary and the royalties from his publications in the United Kingdom to be remitted directly to Paul Ehrenfest. Ehrenfest, in January 1922, wrote to Ein- stein of “Au ions” (i.e., gold ions) and “compounds,” presumably in reference to money and payments. Einstein thoroughly enjoyed these coded exchanges, reply- ing that he had “laughed himself to tears” (Doc. 31). Einstein’s intimate friendship with Ehrenfest remained one of his most crucial relationships. New challenges presented themselves in 1922. In January, Ehrenfest mentioned to Einstein that he might need his moral support in the near future. This appeal may be related to his disclosure, six months later, that his youngest son, Wassily, had been diagnosed with Down syndrome and would be institutionalized at Johannes Trüper’s youth sanatorium in Jena (Docs. 8 and 316). In reply, Ein- stein, in rather unsparing prose, approved of the Ehrenfests’ plan “to hand the child over to impersonal care,” adding “valuable people should not be sacrificed to hope- less causes” (Doc. 329). Ehrenfest also speculated that Einstein did not “need anybody—but I need you very much.” Einstein countered: “I need your friendship as much, perhaps even more, than you do mine for my personal relationships are much feebler and sparser than yours, and I have difficulty finding human contacts that make me feel good” (Docs. 316 and 329). Einstein’s trip yielded important publications in Japan. It occasioned the expres- sion of his now well-known opinion on religion and its relation to science, pub- lished as a set of answers to questions posed by Japanese students. It was written on 14 December 1922 and published in Kaizo in February 1923. Respectful of oth- ers’ beliefs, Einstein nevertheless wrote: “I can regard confessional traditions only historically and psychologically I have no other relationship to them” (Einstein 1923c, Doc. 398). The trip also resulted in the first edition of Einstein’s collected papers, published in Japanese translation. In a preface, Einstein points to the importance for students