James Bruce, Travels to discover the source of the Nile, in the years 1768, 1769, 1770, 1771, 1772 and 1773, Edinburgh 1790, vol. III, pp. 632-644 (describes the place, visited 4-6 November 1770, does not mention the toast)
Miles Bredin, The pale Abyssinian: a life of James Bruce, African explorer and adventurer, London 2000, p. 162 (describes the episode, does not mention this portrayal)
Thomas Wright, The works of James Gillray, the caricaturist, London 1873, appendix pp. 372-374, 'Works, not belonging to the province of caricature or satire, executed by James Gillray as an engraver' (this work not mentioned)
William Schupbach, 'Item of the month – February 2009', Wellcome Library blog, 21 February 2009, archived at : https://wayback.archive-it.org/16107/20210314081756/http://blog.wellcomelibrary.org/2009/02/item-of-the-month-february-2009/
Mark Bills, 'James Gillray; a revolution in satire', Print quarterly, 2023, 40: 353-354 ("an accomplished work displaying Gillray's technical abilities")