Design 51, "The Progress of Poesy", from William Blake's The Poems of Thomas Gray (1797–98).
Featured on PDR in the collection Rainbows in Art
Or, since that hope denied in worlds of strife,
Be thou the rainbow in the storms of life!
The evening beam that smiles the clouds away,
and tints tomorrow with prophetic ray!
(Lord Byron, The Bride of Abydos)