Jamieson, Fausset and Brown on Genesis 50:2

2. Joseph commanded his servants the physicians to embalm his father, &c.--In ancient Egypt the embalmers were a class by themselves. The process of embalmment consisted in infusing a great quantity of resinous substances into the cavities of the body, after the intestines had been removed, and then a regulated degree of heat was applied to dry up the humors, as well as decompose the tarry materials which had been previously introduced. Thirty days were alloted for the completion of this process; forty more were spent in anointing it with spices; the body, tanned from this operation, being then washed, was wrapped in numerous folds of linen cloth--the joinings of which were fastened with gum, and then it was deposited in a wooden chest made in the form of a human figure.