The fastest way was to absorb entire libraries into the collection, advice that Naudé included in his book. Naudé plundered second hand book sellers, and Mazarin instructed his ambassadors, government officials and generals to collect books for him. Naudé was able to travel Europe, and during one trip that lasted several months he collected over 14,000 volumes. By 1648 the library had built up to an estimated at 40,000 volumes. It was open on a regular basis and had built up a sizable number (almost 100) of regular patrons, and several staff members to keep it functioning properly. It became the first in France to be open for all, without references.