[...] I am now scoring The Rhinegold, straight away, with the orchestration. I could find no way of writing the prelude (the Depths of the Rhine) clearly in outline, so I fell back on doing the full score forthwith. It only means that it will take so much the longer to finish—and my head is somewhat confused. [...]
Source: Letters of Richard Wagner, Vol. 1, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 257