Who was the first Pharaoh to be mummified in ancient Egypt?

Answer 1

Osiris, because

Osiris was an earthly ruler, who was popular with his subjects. His brother, Seth, was jealous of this popularity and plotted against Osiris.
Seth's plans to be rid of his brother started when he secretly obtained his brothers measurements and had a magnificent sarcophagus made to fit. This sarcophagus was in the form of a human shaped box. Seth secretly made the sarcophagus to fit Osiris only.
Seth then organised a large feast to which Osiris and a number of others (usually given as 72) were invited. At the height of the festivities Seth produced the sarcophagus and announced that it would be given to whoever it fitted. All the guests tried the sarcophagus for size, but none fitted until finally Osiris stepped into the sarcophagus.
Seth immediately slammed the lid closed and sealed the sarcophagus shut (with molten lead). The sealed coffin was then thrown into the Nile.
Isis was devastated at the loss of her husband and searched for the sarcophagus throughout Egypt and then overseas. She eventually eventually found it where it had come to rest in the roots of a massive tree.
Isis then returned the coffin to Egypt for a proper burial. For safe keeping she concealed it in the marshes beside the Nile.
Unfortunately for Isis Seth found the sarcophagus while out hunting and was so enraged he chopped the body of Osiris into pieces, and scattered the parts throughout the land of Egypt.
Poor Isis had to then set out again looking for the parts of her husband. Eventually she found all the parts except one and reassembled Osiris and wrapped him in bandages. In some accounts Isis breathed life back into Osiris' body and it was then that Horus was conceived. This was a more magical event that it seems, considering the one part of Osiris Isis couldn't find.
This is how the idea of mummifying came up.

Answer 2

Diodorus Siculus, a Greek historian was the first

Answer 3

who was the first perso to find a mummy