“Gerardus Mercator, Evangelicæ Historiæ: Quadripartita Monas Sive Harmonia Quatuor Evangelistarum ("Harmonization of the Gospels") (1592), dedicatory letter. Quoted in Jean Van Raemdonck, Gerard Mercator: sa vie et ses oeuvres (1869), p. 25, footnote 2”

Source: Wikiquote