I read here that in Kabbalistic tradition the four pronged shin (such as that on the tefillin) was once part of the Hebrew Alphabet but was lost, but I was not able to find a source for this tradition. Does anyone here know the source of this tradition?
I found the source for this kabbalistic tradition in the Magen David of the Radbaz. Basically he's using the kabbalistic concept of שמיטין to explain the anomaly of the shin. The idea in short is, that in a previous shemitta (7,000 years) the shin had four prongs, but in the current shemitta it was lost and the shin only has three. According to him that is the reason were missing so many good things in our world.
I'm not sure though if there is an older source for this idea, or if its the Radbaz's own theory. If you know of anything please post as an answer.