Marie d’Harcourt, or Mary of Guelders as she is perhaps better known, was Duchess of Guelders as the wife of Reinald IV, Duke of Guelders and Jülich. They had no children and Marie was widowed in 1423 when her husband died while en route to Castle Rosendael. She remarried in 1426 to Rupert of Jülich-Berg, who was 20 years younger. He died in 1431.
Marie’s date of death is not known. The last mention of her dates from a letter on 9 October 1428. In 1434, she was remembered in a mass so she must have died between those dates.
Her greatest legacy is the prayerbook she left behind. It was copied by Helmich die Lewe, a monk in the Marienborn convent near Arnhem. He completed the work on 23 February 1415. It has almost 600 pages, and over the course of the centuries, many miniatures were cut from the book.
Now Marie’s prayerbook is completely digitalised and available online. This was done as part of a research project led by Johan Oosterman. He said, “The appearance of the book is very beautiful, but its contents are also very deep, it’s probably the most complex prayerbook we know of. Marie must have been a deeply religious person. This book can only be used by someone who demands great things from themselves and who knows how the liturgy works.”