[...] I take the liberty of asking you whether you would care to undertake the design and superintend the making of the costumes for the proposed Festival Performance of my tetralogy, The Ring of the Nibelungs, in the summer of 1876. To give you some preliminary idea of the character of the task, I send you a copy of the dramatic poem, together with certain pamphlets relating to its performance. You will realise at once that it was my perception of the difficulties involved which decided me to seek for an artist particularly experienced and talented in this branch of work.
I regard the problem I have set as offering a rich field for invention, for I actually ask no less than a characteristic picture made up of individual human figures, which will call up before our eyes with arresting vividness the people and events of a bygone culture far removed from the world of our experience. You will also discover very speedily that medieval conceptions of the figures of the Nibelungenlied, which have gained a certain measure of acceptance through the work of Cornelius, Schnorr and others, must be altogether set aside in this instance. On the other hand, recent study of attempts to illustrate specifically northern mythology reveals that the artists have taken refuge in mere reproduction of the classical antique with certain supposedly characteristic modifications. The intimations to be found in Roman writers who came into contact with Germanic peoples as to the costume of the latter do not appear as yet to have found practical application. In my opinion, therefore, the artist who cares to make a study of my subject has a very special field of research and invention open to him, and it would give me great satisfaction to know that this task was in your hands. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 671