"A sarcophagus with this kind of weight and a lid that heavy is made for one reason - to keep whatever spirit in there from ever getting out," a person wrote on Egypt's Ministry of Antiquities (MOA) Facebook page.

The trepidation stems from what's known as the 'Curse of the pharaohs'. The most notable is perhaps that attributed to King Tutankhamun - a number of people involved in the excavation of his tomb in 1922 died early deaths in the following decade.

MOA says the 20-tonne sarcophagus will be opened in the next couple of days. If the world survives, what happens next will depend on what's inside.

"If nothing was found inside the sarcophagus and we did not find any inscriptions on the coffin's body, we will keep it in place until it can be lifted later," MOA spokesman Waad Allah Abu al-Ela told Egypt Independent.

It's the largest ancient coffin ever found in the region. One expert told National Geographic its size suggests it contains the remains of someone very important.

Another said as it was pretty close to the surface it's likely to date to the Ptolemaic period, which ran from 305BC to 30BC. This post-dates the reign of Alexander the Great, but it's possible the sarcophagus was carried from an earlier resting place to where it was uncovered, two millennia later.

But many on social media are hoping for someone who died much more recently.

"They open the mysterious black sarcophagus and inside it's David Bowie, alive and well," wrote Twitter user @iucounu, in a post that's been retweeted thousands of times.

"He then sets about repairing the timeline using the occult knowledge he won through trickery in the Underworld."