With two essentials of civilization, paper and printing-presses, Nuremberg supplied herself at an early day. The first paper-mill in Germany was established here in 1390; and its workmen were obliged to take an oath never to make paper for themselves, nor to reveal the process of manufacture. They went out on a strike when the mill was enlarged, but the authorities imprisoned them until they became docile once more. Koberger's printing-house contained twenty-four presses, and employed over a hundred men, printing not only Bibles and breviaries, but also chronicles, homilies, poems, and scientific works. As the Aldine Press attracted many authors and scholars to Venice, so Koberger's teeming press led several German literati to settle at Nuremberg. For the four first years of Dürer's life, the wonderful mathematician and astronomer Regiomontanus dwelt here, and had no less than twenty-one books printed by Koberger. His numerous inventions and instruments awakened the deepest interest in the Nuremberg craftsmen, and stimulated a fruitful spirit of inquiry for many years. The clockmakers of Nuremberg were famous for their ingenious productions. Watches were invented here in the year 1500, and were long known as "Nuremberg eggs." The modern composition of brass was formed by Erasmus Ebner; wire-drawing machinery also was a Nuremberg device; the air-gun was invented by Hobsinger; the clarionet, by Denner; and the church-organs made here were the best in Germany. There were also many expert metal-workers and braziers; and fifty master-goldsmiths dwelt in the town, making elegant and highly artistic works, images, seals, and medals, which were famous throughout Europe. The most exquisite flowers and insects, and other delicate objects, were reproduced in filagree silver; and the first maiolica works in Northern Europe were also founded here.