The Rath eagerly accepted this noble gift, and hung the two panels in the Rath-haus, sending also a handsome present of money to Dürer and his wife. A century afterwards Maximilian of Bavaria saw and coveted the pictures, and used bribery and threats alike to secure them. In 1627 he accomplished his purpose; and the Rath, fearful of his wrath and dreading his power, sent the panels to Munich. The woodcut portrait of Dürer, dated 1527, shows the worn face of a man of fifty-six years, whose life has been stormy and sometimes unhappy. It is much less beautiful than the earlier pictures, for his long flowing hair and beard have both been cut short, perhaps on account of sickness, or in deference to the new puritan ideas. The face is delicate and melancholy, and seems to rest under the shadow of approaching death, which is to be met with a calm and simple faith. His second book, entitled "Some Instruction in the Fortification of Cities, Castles, and Towns," appeared in 1527, and was dedicated to Ferdinand I., and adorned with several woodcuts. In this the artist showed the same familiarity with the principles of defensive works as his great contemporaries Leonardo da Vinci and Michael Angelo had done. Much attention is paid to the proper sheltering of heavy artillery from hostile shot; and the plans of the towers and bastions about Nuremberg, which were built after Dürer's death, were suggested in this work. A large contemporary woodcut by the master shows the siege of a city, with cannon playing from the bastions, and the garrison making a sortie against the enemy. The celebrated "Four Books of Human Proportion" was Dürer's greatest literary work, and was completed about this time, having been begun in 1523. Its preparation was suggested by Pirkheimer, to whom it was dedicated, and who published it after the author's death, with a long Latin elegy on him. Great labor was bestowed on this work, and many of the original sketches and notes are still preserved. The first and second books show the correct proportions of the human body and its members, according to scale, dividing the body into seven parts, each of which has the same measurement as the head, and then considering it in eighths. The proportions of children are also treated of; and the dogma is formulated, that the woman should be one-eighteenth shorter than the man. The third book is devoted to transposing or changing these proportions, and contains examples of distorted and unsymmetrical figures; and the fourth book treats of foreshortening, and shows the human body in motion. In his preface he says: "Let no one think that I am presumptuous enough to imagine that I have written a wonderful book, or seek to raise myself above others. This be far from me! for I know well that but small and mediocre understanding and art can be found in the following work."