"The quotation was from Shelley's 'Adonais'"
Adonaïs was an elegy written by Percy Bysshe Shelley (1792-1822) following the death of his fellow poet John Keats (1795-1821). Shelley himself died by drowning a year later.
I weep for Adonaïs--he is dead!
Oh, weep for Adonaïs! though our tears
Thaw not the frost which binds so dear a head!
The full elegy Listen on Spotify: Adonaïs