Lake of mirror from beneath, On thee reclines the wet gray cotton sea Glowing faintly overneath Projects penumbras of the tree Pictures alter by the angle Heaven slithers swift as I Near and closely leans in angle Sees thy creature eye to eye Alas! The radiance that makes thee luster Decides to pluck thee bit by bit Pictures fading by the mirror Lake of mirror, be not beat! Keep thy stagnant lake, oh mirror Let thou ripple with some vapor.
This poem describes an object which appears only on a certain natural phenomenon. Try to guess what the object is.