Solved? Mystery of Dr Pepper's secret recipe

A battered notebook discovered in a Texan antiques store could have finally solved a mystery that has baffled generations of sweet-toothed Americans: by what strange alchemy was Dr Pepper first created?

The yellowing pad suggests the distinctive drink was originally concocted from a mixture containing mandrake root and a large quantity of syrup. It was probably sold as a "digestive" to help make stomach medicine palatable.

Bill Waters, a rare manuscripts collector from Oklahoma, stumbled upon the 19th-century sales ledger underneath a wooden, medicine-bottle crate, while he was rooting through a store in the old Wild West town of Shamrock last year. He bought it for $200 (£130), hoping to clean the book up and sell it for a small profit on eBay. However when Mr Waters began researching its contents , he chanced upon a handwritten recipe for a "D Peppers Pepsin Bitter".

Several sheets contained in its pages had letterheads from "W B Morrison and Co. Old Corner Drug Store", a business that existed in nearby Waco at the end of the 19th century. An internet search revealed that the soft drink Dr Pepper was first served at the same store in 1885."I started saying to myself, 'Wait a minute'... I began feeling like I had discovered a national treasure," said Mr Waters, 59.

Next week, the faded piece of American culinary heritage, which measures 8.5in by 15.5in and is roughly 360 pages long, will be sold at the Dallas-based Heritage Auction Galleries. It has been listed with an estimated value of $50,000 to $75,000. Faded letters on its brown cover say that it contains "Castles Formulas". John Castles was a partner at Morrison's for a time and was a drugist at the store as early as 1880, according to Mary Beth Webster at the Dr Pepper Museum and Free Enterprise Institute.

Today, the sweet-but-spicy drink which descended from the recipe Mr Castles noted down is part of the Dr Pepper Snapple Group, and is distributed across several continents. Dr Pepper is made from a top-secret combination of 23 different ingredients and the exact combination is only made known to three senior employees of the firm at any one time.

Though it does not dispute the book's authenticity, they believe that the recipe it contains – which is partly illegible – is for a medicine rather than a soft drink. A spokesman for the firm told the Associated Press that it bore little resemblance to the real Dr Pepper recipe.