This was Scott's first public appearance following his woes. The stone postdates the funeral by a century. Professor John Playfair (1748–1819) was an important mathematician and scientist of his day. He was brother to architect James Playfair and engineer William Playfair, as well as uncle of the architect William Henry Playfair. He was a close friend of James Hutton. Originally unmarked, his grave, immediately adjacent to Yelin's, was marked by a plaque unveiled in 2011. Playfair's monument (designed by William Henry Playfair) stands on Calton Hill rather than on his grave, and can be seen from the north section of the graveyard. Peter Williamson (1730–1799), nicknamed "Indian Peter", was a colourful character born near Aberdeen. He was kidnapped and sold into slavery at the age of 13, and is one of the few well-documented examples of the early white slave trade. Around 10 percent of slaves were white, although they and their descendants normally found it easier to escape the circle of slavehood in later generations. Peter escaped, and lived with Native Americans ("Indians") for some years (hence his nickname). He returned to Scotland and successfully sued Aberdeen Town Council for its part in his enslavement. This made him into a relatively rich man for his day. Partly backed by this cash he set up several enterprises, most notably the first Edinburgh Penny Post in 1773, which was usefully linked to one of the world's first street directories. He is buried in the Scott family grave along with his daughter Agnes Williamson Scott who married into the Scott family, however Peter Williamson's name does not appear on the monument. Sir John Steell (1804–1891) acclaimed Scottish sculptor is buried in an unmarked grave in one of the family vaults to the side. Other burials include James Lumsden (1836–1899), a well-known singer of his day, Richard Dickson (1792–1857) architect, William Sibbald (d. 1809) architect, Robert Kay (1740–1818) architect, and Prof George Wilson MD (1818–1859), a text book author and biographer. Betty Morton's monument was erected by Archibald Campbell Tait (1811–1882), Archbishop of Canterbury, in memory of his nanny. Iron tablets, such as the one to John and David Paton (builders of much of the Edinburgh New Town), c1830, were in vogue for a decade or two, and it was not realised how badly these items would weather.