Embalming was not fully developed until the New Kingdom (1587-1087 BCE). The complete process took about 70 days. The full treatment included cleaning the body, removing the organs, cleaning it again, drying it with natron (which is the key element in preservation), oiling the skin, replacing external parts such as eyes, and then finally wrapping it and placing it in a coffin. The only organ that was left in was the heart, which was believed to contain the soul. The liver, the lungs, the stomach, and the intestines were place in separate jars called "Canopic Jars". These Canopic Jars were for means of protection. A ritual accompanied every aspect of embalming. The most important ceremony was called the "Opening of the Mouth", in which the priest gave "life" to each part of the mummified body by touching it with a sacred instrument.
The most important aspect of this burial tradition is the "Opening of the Mouth" ritual. Before the burial, "Opening of the Mouth" was performed on the mummy of the deceased. The priest would open the mouth of the mummy with a tool so the mummy could speak and eat the funeral meal. Oddly they believed that the wall scenes and the statues of his family, servants would come to life. Inside the tomb would also be a depiction of a boat, which was believed to come to life as a full sized vessel that could sail the Nile. All the people and activities shown on the wall scene would become real for eternity to bring happiness to the tomb owner. .
The theory behind mummification was at death the Egyptians believed that their personality would separate from the body and was free to travel, but it still had a link with the body in the tomb. However, this was not guaranteed unless the ritual was properly performed and all material provisions were made in the tomb for the afterlife. Filling the man's tomb with food and beverages was mainly the duty of his descendants.