Dio Chrysostom, On Training for Public Speaking 4

Writing, however, I do not advise you to engage in with your own hand, or only very rarely, but rather to dictate to a secretary. 

For, in the first place, the one who utters his thoughts aloud is more nearly in the mood of a man addressing an audience than is one who writes, and, in the second place, less labor is involved. 

Again, while it contributes less to effectiveness⁠ in delivery than writing does, it contributes more to your habit of readiness. But when you do write, I do not think it best for you to write these made‑up school exercises; yet if you must write, take one of the speeches that you enjoy reading, preferably one of Xenophon's, and either oppose what he said, or advance the same arguments in a different way. 

And yet repeating what his speeches contain is better still if you have a good memory for it. For this makes one thoroughly familiar with both the way he expresses his thoughts and the accuracy with which his thoughts are conceived. 

I say this, not to encourage you to string together line for line an entire treatise, as schoolboys do, but that you may thoroughly master anything that happens to please you especially. I should have written at great length about this to a lad, but for you, this much is sufficient. For if you call to memory only very small portions, you will derive great benefit; whereas if you should feel disinclined and find the effort painful, this work is not absolutely necessary. 

Well, I seem to have extended my advice to great length, but you yourself are to blame for that by persuading and challenging me. Just as expert wrestlers sometimes give way to those who are weaker and make them believe that they are stronger, so you seem to have led me on to write and tell what you, as it happens, know better yourself, just as if you did not know it so well. 

But I should prefer, if it proved agreeable to you, that we should get together some time and by reading the ancient writers and discussing them render some service to each other. 

Just as it is not enough to say to painters and to sculptors⁠ that their colors should be just so and that their lines should be just so, but they derive the greatest help if the critic can see them at work, painting or modeling; and just as it is not sufficient for the gymnastic masters to name the different holds in wrestling, but they must go on and demonstrate them to the youth who wishes to learn; so too in consultations like this, the help would be greater if one were to see the man who has given the advice in action himself. 

I declare for my part that even if I had to read aloud to you while you listened, for the sake of helping you I should not hesitate, since I both love you and admire you for your ambition, and am grateful for the honor you have shown me.