Robert Burns's diamond point engravings
Robert Burns came to know James Cunninghamme, Earl of Glencairn in Edinburgh in 1786 through a 'Letter of Introduction' provided by Dalrymple of Orangefield who was married to Lady Glencairn's sister. The Earl received the poet warmly in his house and introduced him to his friends.
Source: Wikipedia — Robert Burns's diamond point engravings (CC BY-SA 4.0)