This work describes the orthographic content in grammars of European languages in the 17th and the 18th century. Reviewed were 17 grammars for 7 languages in Rationalism, 15 grammars for 11 languages in the Enlightenment, and 12 Latin orthographies. As for orthographic entities in the broader sense (orthography as a way to write down speech), our starting point were orthographic grapheme units which are contrasted to meaning (i.e. orthographic entities in the narrower sense, e.g. punctuation). Contrary to the traditional description which focused on spelling, this work observes the beginnings of orthographic content in grammars and its development into an autonomous language phenomenon and norm. The strong connection between orthography and grammar is described and it is established that, from the diachronic point of view, orthography cannot be integrally reviewed without studying the grammatical teachings.