Gottfried Wilhelm Leibniz to Simon Foucher, 1675:
As for myself, although I always liked to meditate, I always found it difficult to read books that cannot be understood without much meditation. For, when following one's own meditations one follows a certain natural inclination and gains profit along with pleasure; but one is enormously cramped when having to follow the meditations of others. I always liked books that contained some fine thoughts, but books that one could read without stopping, for they aroused ideas in me which I could follow at my fancy and pursue as I pleased. This also prevented me from reading geometry books with care, and I must admit that I have not yet brought myself to read Euclid in any other way than one commonly reads novels [histoires]. I have learned from experience that this method in general is a good one; but I have learned nevertheless that there are authors for whom one must make an exception – Plato and Aristotle among the ancient philosophers and Galileo and Descartes among ours. Yet what I know of Descartes's metaphysical and physical meditations is almost entirely derived from reading a number of books, written in a more familiar style, that report his opinions. So perhaps I have not yet understood him well.