The Speculum Humanae Salvationis or Mirror of Human Salvation was a bestselling, anonymously illustrated work of popular theology in the late Middle Ages, part of the genre of encyclopedic speculum literature, in this case concentrating on the medieval theory of typology, whereby the events of the Old Testament prefigured or foretold the events of the New Testament. The original version is in rhyming Latin verse, and contains a series of New Testament events each with three Old Testament ones that prefigure it. It is one of the most common books found as an illuminated manuscript, and also in early printing in both blockbook and incunabulum forms.