We describe a basic 'cross-over' trial undertaken by Sir Nicholas Gilbourne of Kent, England, in or before 1631. This was used to test the effectiveness of 'weapon salve', an ointment claimed to cure 'sympathetically' (i.e. remotely) by application to the weapon that inflicted an injury. Gilbourne reports very basic outcomes but these represent key stages of a modern cross-over trial: no treatment, treatment, no treatment, treatment. We discuss the value of such historical vignettes - even a magical one - for medical students in two respects: understanding research methodology and learning about consultation strategies. Gilbourne's conclusion is clearly fanciful but the basic principles behind his experiment are sound. Historical examples like this can inspire medical students to think critically about research methods and treatment strategies.
Keywords: Seventeenth century; controlled trials; cross-over trials; fair comparison; magic; n=1 studies; weapon salve.