Battista Guarino, de ordine docendi et studendi XXX:
“Students should not be content simply to hear lectures from a teacher; they should also read the approved commentaries written upon these authors. They should read these works for themselves thoroughly, and note their thoughts and the strength of their words all the way to the roots, as they say. They should look for new expressions which are suited to particular occasions. It is also extremely useful to write explanations in the margins of the books, all the more so if they think that they will bring them forth ‘into the light’ someday. We are, indeed, more attentive to those things from which we hope to earn some praise. This type of exercise does wondrous work of sharpening the intellect and polishing the tongue; it produces a promptitude in writing, brings forth a more perfect knowledge of the world, it confirms the memory, and offers students something like a ready storehouse of explanation and an aid to memory.”
Mark Pattison says that reading commentaries for himself went a long way in his days as a student
Nec sint solum a praeceptore audire contenti, sed qui in auctores commentaria scripserunt et probati sunt, eos ipsimet perlegant et radicitus, ut aiunt, sententias et vocabulorum vim annotent. Novas ipsi sententias et ad rem accomodatas exquirant. Explanationes quoque in libros scribere vehementer conducet, sed tamen magis si sperabunt eas in lucem aliquando prodituras. Attentiores enim ad ea sumus, ex quibus laudem venari studemus. Hoc exercitationis genus mirifice acuit ingenium, linguam expolit, scribendi promptitudinem gignit, perfectam rerum noticiam inducit, memoriam confirmat, postremo studiosis quasi quandam expositionum cellam promptuariam et memoriae subsidium praestat.