The believed that the deceased continued to live on in a parallel existence with the living, often in the form of mummies

The answer is Egyptians. Since it was measured essential for the existence of the soul, protection of the body was a dominant part of Egyptian funerary practices. Initially the Egyptians concealed their dead in the desert, where the dry circumstances mummified the body logically. Tombs could cover a countless variety of other items because it was supposed that the dead would have to do work in the life after death.