This volume bears the Irish name for the the "Land of Youth," the realm of Faerie. It collects fairy and troll themed paintings by French artist Georges Reynolds, with a few pencil works scattered throughout. This one has an accompanying caption:
"Lorelei is a very ancient aquatic nymph who inhabits the waters of the Rhine. She does not have a fish tail like her sisters the Nixies or Ondines, but that does not diminish her grace or speed. In her splendid underwater palace, Lorelei welcomes and consoles those in despair. Just as much compassion touched the heart of a young then-unknown musician named Richard Wagner who composed a delicate ode in homage to her goodness and beauty."
In the real world, Lorelei (meaning "Murmuring rock") is a cliff on a tricky turn in Germany's Rhine River. Its bowl shape amplifies the murmur of a waterfall on its surface, hence the name.
Between this sound and the rock's propensity to wreck boats, poems and songs about an enchanting "Lore Lay" or "Lorelei," living on the rock and luring sailors to their doom, peppered nineteenth century German culture, including a setting by Franz Liszt.
Wagner included three water spirits (German Nixen) whom he described as "Rhinemaidens" (Rheintöchter) in his opera cycle "Ring of the Nibelung," though he named them Woglinde, Wellgunde and Floßhilde. Wagner specified that they should appear to be underwater, which naturally poses a challenge to stage productions. This 2007 production of Das Rheingold puts them in actual water, at least halfway. I cannot find a Lorelei example from Wagner from when he was “young” and “unknown” as Reynolds claims.