Ancient Writing Texts

I've been thinking some about writing instruction, looking at various books and curricula, reading reviews, etc.  In the process I came across Progymnasmata: Great Textbooks of Prose Composition and Rhetoric.  The book consists of English translations of four ancient Greek composition textbooks.  In each, the progymnasmata is explained and in some of the texts examples are provided.  Most of the greatest authors (or just about any writer or speaker) from before the time of the New Testament until the modern period would have used one of these texts or one similar.

Here are a couple of quotes from The Exercises of Aelius Theon.  First on the progymnasmata in general:

These things are, as it were, the foundation of every kind of discourse, and depending on how one instills them in the mind of the young, necessarily the results make themselves felt in the same way later.  

And this good advice on making corrections to a student's writing:

The making of corrections (by the teacher) in the early stages of study is not aimed at the removal of all mistakes but at correction of a few of the most conspicuos in such a way that the young man may not be discouraged and lose hope about future progress.