Work brought me to Prague today. I found a nice place to stay, in a lively area of Prague, just outside the old city, in Havelská (street).
This is the street where Mnisowsky used to live. His house is just one block away, and I believe it is this one.

   

Just round the corner is the house where Marci lived. His bust was attached to the building on the instigation of the historian Josef Smolka:

   

Thank you! It's a pleasure to see these and to put a "face" to the mystery's history.

I made it as far as the east Hungarian border and also quite a distance into eastern Germany, and I spent a day in Austria, but time constraints made it impossible for me to see Prague, which I deeply regret, so I am thrilled that you are sharing these images.