English interpretation of Clausewitz' account of the combat of Prenzlau (28 October 1806) can be found in this book:
The Jena Campaign: Source Book, Fort Leavenworth, Kansas, 1922, p. 604-611.

https://books.google.ru/books?id=TApXpwAACAAJ

Clausewitz doesn't mention that the first rank knelt, he says that the Prussians were formed in a 3-rank square "according to the old method".