The science journalist Matt Kaplan starts and ends his book The Science of the Magical with quotes from the royal elf Galadriel from The Lord of the Rings.
The one in the beginning:
And some things that should not have been forgotten, were lost. History became legend and legend became myth.
Galadriel says this in the movie The Fellowship of the Ring about the evil One Ring, which had been forgotten by many beings at the beginning of the story. Similarly, Kaplan says, many truths found in old magical stories have been relegated to myths.
The book itself is a hodgepodge compendium of different magical beliefs throughout history, separated into chapters by topic, like prophecies, enchantments, and magical healing. With each, Kaplan investigates what was actually happening and finds that many magical practices actually had a basis in science. For example, the magical healing power of hot springs like the one at Bath makes a lot more sense when he points out that cold suppresses the immune system, and before central heating people were cold a lot (those far from the equator, at least). A warm spring probably did our frequently-freezing ancestors a world of good.
For other myths, the science is more speculative. Kaplan considers how things that were once the stuff of legends could one day become reality. Turtles and tortoises live an incredibly long time, and while eating them does not lead to immortality as some once believed, some scientists suspect that turtles have high levels of antioxidants in their bodies, helping to prevent DNA damage and allowing them to live longer. Similarly, Kaplan reports, a drug that increases production of an antioxidant enzyme in humans and helps protect cancer patients from radiation could possibly help protect against the chemicals that make us age, too. So the turtles held a clue after all.