Sophie wrote the following to Lieselotte's sister Karoline (June 1687):
Der gutte Courprins bekombt aber ein hauffen böe brif von Dero Herr Vatter, welger I. L. verfluchen wollen, wan sie nicht widerum nach Berlin gehen, welches I. L. gern thun wolten, wan die poudre de succession nicht thar ihm schwang ging undt I. L. schon selber in gefhar tharvon weren gewessen‚ aber doch durch ein hauffen contrepoisen sein errett worden undt sich nun gottlob recht wol befinden.
[ETA: English translation, because that's not exactly easy German: The good electoral prince [?] is getting a lot of angry letters from his father, who wants to execrate him if he doesn't go back to Berlin. Which the prince would like to do if there wasn't succession powder [nice] going around and if he hadn't been in danger himself already, getting rescued through a bunch of antitoxin and feeling well now, thank God.]
See here, page 48, and it looks like there's also a Lieselotte letter on the topic, but not quoted. The book is a dissertation about the Schwedt line and unfortunately, the poisoning chapter has inconvenient gaps in the google preview, but it's clear that the author thinks it's all BS and Dorothea was unfairly judged in general. He also isn't a big fan of F1 or Sophie it seems, but the book might still be worth a look at some point, not least because he seems to have included a lot of unpublished letters from the state archive.
Re: Pöllnitz: Secret Keeper?
Der gutte Courprins bekombt aber ein hauffen böe brif von Dero Herr Vatter, welger I. L. verfluchen wollen, wan sie nicht widerum nach Berlin gehen, welches I. L. gern thun wolten, wan die poudre de succession nicht thar ihm schwang ging undt I. L. schon selber in gefhar tharvon weren gewessen‚ aber doch durch ein hauffen contrepoisen sein errett worden undt sich nun gottlob recht wol befinden.
[ETA: English translation, because that's not exactly easy German: The good electoral prince [?] is getting a lot of angry letters from his father, who wants to execrate him if he doesn't go back to Berlin. Which the prince would like to do if there wasn't succession powder [nice] going around and if he hadn't been in danger himself already, getting rescued through a bunch of antitoxin and feeling well now, thank God.]
See here, page 48, and it looks like there's also a Lieselotte letter on the topic, but not quoted. The book is a dissertation about the Schwedt line and unfortunately, the poisoning chapter has inconvenient gaps in the google preview, but it's clear that the author thinks it's all BS and Dorothea was unfairly judged in general. He also isn't a big fan of F1 or Sophie it seems, but the book might still be worth a look at some point, not least because he seems to have included a lot of unpublished letters from the state archive.