Osiris mysteries were celebrated at other places, at least in later times and perhaps even in the Middle Empire; but it is not easy to discern the part these mysteries played in the Middle Empire in the beliefs of the common people regarding their immortality. The Osiris story was one of the most widespread in Egypt, and, powerful in its effect on the feelings of all classes, was certain, sooner or later, to prepare the way for a general belief in a better immortality; but if we may judge from the burial customs, the great mass of the people still believed merely in an underworld, Earu, a duplicate of the earthly life, but with greater possibilities of danger and evil. During the course of Egyptian history the position in which the body is buried undergoes a series of remarkable changes. During the early pre-dynastic period, the body, loosely enfolded in cloths and skins, is laid in the grave double up on the left side, _usually_ with the head south (i.e. upstream). This position becomes the custom, with very few exceptions, during the late predynastic period and the first three dynasties. Throughout the Fourth to Sixth Dynasties, the body was in the same position, but with the head north, loosely covered with shawls and garments. The crouching position, with some slight modifications, continues to be used for the poorest class down to the New Empire. Among the Nubians, it is universal to the New Empire and customary even later in unmixed Nubian communities. The swathed extended burials begin in Egypt in the Fourth Dynasty, so far as remains are preserved. Some members of the royal family of Cheops were buried in swathed wrapping, lying extended on the left side with the knees bent. During the Fifth and Sixth Dynasties this extended position on the side becomes customary for the better classes; and during the Middle Empire it becomes almost universal. The final burial position, the swathed mummy lying extended on the back, does not become general until the New Empire, about 1600 B.C. although it is the position hitherto regarded as the characteristic Egyptian burial position. A few isolated cases, some of them perhaps accidental, occur as early as the Old Empire; but in the New Empire the extended burial on the back is practically the only one to be observed. In other words, beginning in the predynastic period with a burial position which may be called natural and primitive, the Egyptian gradually adopted a position which imitated the form of the dead Osiris, the god of the dead. Each new change is first adopted by the royal family, and is taken up by the other classes in turn until it becomes universal. In the final form, the mummy was a simulacrum of the dead as Osiris.