“World's oldest photo sold to library”. BBC News (Thursday, 21 March, 2002). 2011年11月17日閲覧。 “The image of an engraving depicting a man leading a horse was made in 1825 by Nicephore Niepce, who invented a technique known as heliogravure.”
“The First Photograph — Heliography”. 2009年9月29日閲覧。 “from Helmut Gernsheim's article, "The 150th Anniversary of Photography," in History of Photography, Vol. I, No. 1, January 1977: ... In 1822, Niépce coated a glass plate ... The sunlight passing through ... This first permanent example ... was destroyed ... some years later.”
