In an undated letter to unpaid assistant Anton Schindler (whom he refers to as “signore povero Papageno”) that appears to be sent during his stay in Hetzendorf, Beethoven says since he has not seen his unpaid assistant today, he should wait for the housekeeper, Barbara Holzmann, who is going into the City tomorrow morning, and then he can tell her whether he is coming later, or he can come with her. He says “it is highly necessary.” He signs it, “poor beaten-down B—n.” Schindler writes back on the letter with pencil (which apparently was returned by Holzmann without Schindler). He was unable to come to visit before today, even though the weather was good, since he has had rehearsals at the Theater in the Josephstadt from 8 AM until 3 in the afternoon every day for the whole week (which suggests that this letter was sent towards the end of the week, perhaps on a Friday or Saturday).
Brandenburg Letter 1654, Anderson Letter 1222. The original is held by the Berlin Staatsbibliothek (aut. 36,49).