[ London Times ]
This newspaper, most correctly known simply as The Times, began publication in 1785 and continues to this day.
The September 2, 1819 edition of The Times carried the following "for sale" notice:
DOGS to be DISPOSED OF, at STEPHENSON'S MENAGERIE, New-Road, Somers-town, near Battle-Bridge, a warranted good retriever of the Newfoundland breed. . . [and] several Newfoundland bitches and whelps. Dogs cured of every disease.
That this dog is identified as a 'Newfoundland retriever' is not necessarily an indication it is a mix. Breed classifications and relationships were in flux for much of the 19th Century.