Idleness and translation exercises
Quaeris quemadmodum in secessu, quo iam diu frueris, putem te studere oportere. Utile in primis, et multi praecipiunt, vel ex Graeco in Latinum vel ex Latino vertere in Graecum. Quo genere exercitationis proprietas splendorque verborum, copia figurarum, vis explicandi, praeterea imitatione optimorum similia inveniendi facultas paratur; simul quae legentem fefellissent, transferentem fugere non possunt. Intellegentia ex hoc et iudicium adquiritur.
You ask me what course of study I think you should follow during your present retirement. The most useful thing, recommended by everyone, is to translate Greek into Latin and Latin into Greek. This kind of exercise develops a precise and resplendent vocabulary, a variety of figures, and the power of exposition, and imitation of the best models improves your ability to write your own texts. Also, any point which might be overlooked in mere reading cannot escape the eye of a translator. This method lets you acquire knowledge and judgement too. (my translation, cribbed from Betty Radice and William Mormont)
Of course, in my experience in the business world of translation and in the literary one, if you can’t already write well in the target language, you can’t really translate very well, because you can’t think. We think only by using “our” language, “our” in this case being the defective version each of us hold, differently, of our mother or most commonly used tongues. The more restrained "our language" is, the more difficult it is to perform that act called reading. So the retiring student may not progress in translation as far as Pliny imagines.
I prefer to think of this as a paradox rather than as a contradiction. For Pliny is right, really. It’s worth translating anyhow, whether you try it word for word (trying to reproduce the value of the coin) or movement by movement (trying to transmit the weight and temperature of the coin) for it teaches you endlessly about your mother tongue: weight, temperature, value.