For this purpose he borrowed a set of prisms from a friend living in near-by Jena, the physicist, Büttner. Since, however, he had at that time no opportunity of arranging a dark chamber on Newton's lines, where the necessary ray of light from a tiny hole in the window-covering was sent through a prism, he postponed the whole thing, until in the midst of all his many other interests and duties it was forgotten. In vain Büttner pressed many times for the return of the prisms; at last he sent a mutual acquaintance with the injunction not to return without them. Goethe then searched for the long-neglected apparatus and determined to take a rapid glance through one of the prisms before he gave them back.