"The quotation was from Shelley's 'Adonais'"
John Keat's tombstone, Protestant Cemetry, Rome
GNU Free Documentation LicenseJohn Keat's tombstone, Protestant Cemetry, Rome - Credit: Piero Montesacro, Wikimedia Commons

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