Lockhart, Will. The Secrets of Advanced Prestidigitation. Plaistow: W. Bull, 1894. Decorative printed wraps. 8vo. p.  3—29 (pp. 13—29 being “Abridged Catalogue of Novelties in Conjuring Tricks and Magical Apparatus by Lockhart & Co.”). Tipped-in letter from Lockhart to an inquirer discussing his “arrangements with a gentleman, a mechanic who has for the past 20 years been in the employ of a London Conjuring Maker now deceased”.