I have ample reason to believe that sarcophagi were used for 3 purposes.

1. "Initiation" aka activation of higher chakras. Sarcophagi were used as sensory deprivation chambers. Bentov's work validates this idea scientifically, as does work done on sensory deprivation chambers showing they produce theta waves. In the appendix of Stalking the Wild Pendulum, he said the frequencies like 4 or 7 Hz can spontaneously trigger kundalini awakenings.

2. "Healing" in the form of past life memory exploration. This can be cathartic in a number of ways. People often behave in ways that carry over from a previous life. Understanding some of that can be healing. Also, just realizing that one has had past lives helps one understand that one will have future lives and so fearing one's own mortality is a bit unnecessary. Both the reincarnation research out of Univ of VA's Med School and the work of Dolores Cannon support this when juxtaposed with known scientific research on children's brain wave states prior to age 7, i.e. theta waves.

3. Fancy burial vessels for the people who owned that sarcophagus and used it as their own personal sensory deprivation chamber.

In the Law of One, Ra says the pyramids were primarily used for healing and initiation in the kings and queens chambers respectively.

In 3.16, Ra says that the first use of the pyramid was for sensory deprivation.

I searched the Law of One for the word "sarcophagus" and got one single hit on 80.20 which is about Tarot Card 20. I looked it up in my Kabbalah/Tarot textbook resource and it said that card, called "The Great Awakening" is all about death. Bear in mind the etymology of sarcophagus is "being eaten by stone".

Death...da'ath.

Potayto...potahto.

In Kabbalah, activation of the wisdom chakra, Vishuddha, in the throat, aka gnosis, is called "da'ath". Da'ath means "knowledge". When one "achieves" da'ath, one is typically described, by those who knew them beforehand, as being reborn...almost a different person.

Born again, da'ath/rebirth, Phoenix rising from it's own ashes, dark night of the soul...these all echo the idea of the dissolution of the self or, in this translation, that the stone was eating the self.

It all lines up :)