This is the quote from Mircea Eliade's Ordeal by Labyrinth : Conversations with Claude-Henri Rocquet (pp. 37-38):
R. How did you set about learning Sanskrit, first with him, then with the pandit?
E. Well, as far as learning Sanskrit is concerned, I applied the method of the Italian Indianist Angelo de Gubernatis, which he describes in his autobiography, Fibra. It consists in working for twelve hours a day with a grammar, a dictionary, and a text. That’s how he did it himself, in Berlin. Weber, his teacher, had said to him (this was in early summer): “Gubernatis, here is the situation: my Sanskrit course starts in the fall, but it’s a second-year course, and we can’t start at the beginning again just on your account. So you’ll just have to catch up.” Gubernatis shut himself away in a summer cabin, just outside Berlin, with his Sanskrit grammar and dictionary. Twice a week someone came to deliver bread, coffee, and milk. He was right, and I followed his example. Besides, I had already gone through two similar experiences, not quite so extreme, but still. . . . When I was learning English, for example, I used to work for several hours nonstop. But this time, right from the outset, I worked for twelve hours a day and on nothing but Sanskrit. The only exceptions I made were to take a walk now and then and to use my tea and meal breaks for improving my English: I could read it very well, but I still wasn’t very good at speaking it. And while I was at Dasgupta’s house, he would occasionally put questions to me or give me a passage to translate, just to monitor my progress. And, if it was rapid, I believe that was the result of my determination to study nothing other than Sanskrit. For a period of several months I didn’t so much as pick up a newspaper or a detective novel— anything. And that exclusive concentration on a single object, Sanskrit, produced amazing results.
R. All the same, isn’t there a risk, using that method, of failing to acquire the subtlety and flexibility of the spoken language?
E. Certainly. But at the outset it was a matter of acquiring solid foundations, of absorbing the grammatical structures and concepts, the basic vocabulary. Later on, naturally, I applied myself to Indian history and aesthetics, to poetry and the arts. But to begin with, it is essential to aim at a methodical and exclusive acquisition of the rudiments.