TITLE: Oldest photographed mathematician
QUESTION [11 upvotes]: Who is the most ancient mathematician of which we have a photograph? 
(or, in the same vein, what is the oldest photograph of a mathematician) 
A quick search on MacTutor History of Mathematics gives Binet (b.1786) as a pretender with Cauchy (b.1789) coming close...

REPLY [27 votes]: Most ancient: Wikipedia has a daguerreotype of Gauss (1777–1855) on his deathbed. Or possibly Farkas Bolyai (1775–1856) in what look like similar circumstances.
Less ancient, but allegedly photographed earlier: Googling "daguerreotype mathematician" gives
• c. 1840, 1840: Augustus De Morgan (1806–1871)
• c. 1842–1843: Ada Lovelace (1815–1852)
• c. 1843: Friedrich Wilhelm Bessel (1784–1846)
• c. 1843: Joseph Plateau (1801–1883)
• c. 1843, 1847–1851: Charles Babbage (1791–1871)
• c. 1844: William Henry Fox Talbot (1800–1877)
• c. 1845: François Arago (1786–1853)
• c. 1845: William Rowan Hamilton (1805–1865) (per frontispiece)
• c. 1846: William Thomson (1824–1907)
• c. 1846: John Couch Adams (1819–1892)
• c. 1847: Hermann von Helmholtz (1821–1894)
• c. 1848: John Herschel (1792–1871).