This article explores the problematic issue of using editions as sources for studies of English historical morpho-syntax. It presents a methodological case study of the variation between he and it in reference to inanimate objects (such as mercury) in Mirror of Lights, an alchemical text that survives in multiple copies from the 15th and 16th centuries. The study reveals that the manuscript versions differ greatly in how they employ he and it, underscoring that linguistic studies based on one version would provide very different results from those using another version as the source. The article argues that it is crucial that such manuscript variation is taken into consideration in morpho-syntactic studies. It suggests that an electronic edition that incorporates all copies of the text would make the full variation available to linguists, while a traditional critical edition would highlight the pattern of one version but obscure or ignore the patterns of other manuscripts. The article also discusses the more general problem of including a multiversion text such as the Mirror of Lights into a corpus, and suggests some possible solutions.