The Speculum Humanae Salvationis or Mirror of Human Salvation was a bestselling anonymous 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. After a short Prologue (two pages) and Prohemium (four), both unillustrated, the first two chapters deal with the Creation, the Fall of Satan, the story of Adam and Eve and the Deluge in four pages. Then follow forty more double-page chapters where a New Testament event is compared with three from the Old Testament, with four pictures each above a column of text. Usually each chapter occupies one 2-page opening. The last three chapters cover the Seven Stations of the Cross, and the Seven Joys and Sorrows of Mary, at double this length. In all, a complete standard version has 52 leaves, or 104 pages, and 192 illustrations (including a blank page at the beginning and end). The blockbook editions were much shorter, with 116 pictures, two to a woodblock. The writing of the text follows an exact scheme: twenty-five lines per column, with two columns per page, one under each miniature, so a hundred lines per standard chapter. Sometimes there are captions over the pictures as well, of varying content. Many copies reduced the original text, often by omitting the non-standard chapters at the beginning or end, whilst others boosted the content with calendars and commentaries, or extra illustrations. The work originated between 1309, as a reference to the Pope being at Avignon indicates, and 1324, the date on two copies.