Meanings
off one's own bat, on one's own hook (on one's own, without aid or oversight by others, especially from those more experienced or powerful)
Hierauf folge aber weiter nichts, als daß dem zügellosen Projektanten das fernere unnöthige Bauen, jedoch mit Ausnahme einer auf eigene Faust schon zu bauen angefangenen Mühle, ganz gelind gesagt verbothen, oder vertraulich misrathen wurde; […]But this was not followed by anything, except that the inordinate planner was, to put it mildly, banned, or dissuaded in private, from further needless construction work, however with the exception of a mill whose construction had already been started on personal initiative; […]