With the much heralded publication of Dan Brown's The Lost Symbol this week, it was discovered that there are quotes from, references to or concepts explored in six titles published by Penguin Group (USA)'s Tarcher imprint throughout the book. The Epigraph that precedes the first page is a quote from Manly P. Hall's The Secret Teachings of All Ages: "To live in the world without becoming aware of the meaning of the world is like wandering about in a great library without touching the books." That book is also quoted and the author credited on page 501: "If the infinite had not desired man to be wise, he would not have bestowed upon him the faculty of knowing."

According to Tarcher Publisher Joel Fotinos, "[The Lost Symbol] discusses many esoteric philosophies and concepts - it essentially could be subtitled: ‘A Tarcher Reader.' The concepts are throughout the book in general and relate specifically to the plot of the book - and nearly all the esoteric concepts are found in The Secret Teachings of All Ages."

Another Tarcher title specifically referenced is The Kybalion. And concepts in The Lost Symbol are well-discussed in further Tarcher books: Manly P. Hall's The Lost Keys of Freemasonry and The Secret Destiny of America, as well as Hermetica: The Lost Wisdom of the Pharoahs by Timothy Freke and Peter Gandy and The Kabbalah Handbook by Gabriella Samuel. So if readers of The Lost Symbol want to find the true stories behind the novel, all of these Tarcher titles are must reads.