While studying the bookbinding of an incunable, we discovered that the initially indistinct pattern within the diamonds is actually a heart pierced by an arrow! Today, we may associate this symbol with lovers, but in this case, it is most likely a Christian symbol, referring to the Sacred Heart of Jesus.
The book contains a text by the Roman Catholic theologian and mystic Dionysius Carthusiensis and was printed in Nuremberg in 1495, with a contemporary binding.
Many thanks to Professor Konstantinos Choulis and conservator Andreas Fatouros for this discovery!