Plato’s Myth of Er and the Waters of Forgetfulness (Lethe)
In the Republic, souls preparing for rebirth must drink from the River of Lethe. The more they drink, the more they forget their divine origin. Souls then choose a new life on earth—some noble, some humble—based on their degree of forgetfulness.
"I am a child of Earth and of Starry Heaven; But my race is of Heaven (alone). This ye know yourselves. And lo, I am parched with thirst and I perish. Give me quickly The cold water flowing forth from the Lake of Memory."
a password or Totenpass (pass of the dead) from the Orphic Gold Tablets, specifically found on a lamella from Petelia in Southern Italy (4th–3rd century BCE).
The inscription served as a ritual declaration for the soul in the Underworld, guiding it to avoid the Spring of Forgetfulness (Lethe) on the left and instead drink from the Lake of Memory (Mnemosyne) on the right.
By reciting this password and drinking from Mnemosyne, the initiated soul was granted lordship among the heroes and freedom from the cycle of reincarnation.