This tattered old ledger book filled with formulas was discovered at an antique store in Waco, Texas, and might contain an early formula for Dr Pepper.

DALLAS — Poking through antiques stores while traveling through the Texas Panhandle, Bill Waters, 59, stumbled across a tattered old ledger book filled with formulas.

He bought it for $200, suspecting he could resell it for five times that. Turns out, his inkling about the book's value was more spot on than he knew. The Tulsa, Okla., man eventually discovered the book came from the Waco, Texas, drugstore where Dr Pepper was invented and includes a recipe titled "D Peppers Pepsin Bitters."

When the 8Z\x-by-15Z\x inch book of more than 360 pages goes up for auction at Dallas-based Heritage Auction Galleries on May 13, it's expected to sell for between $50,000 and $75,000.

Waters discovered the book, its yellowed pages stained brown on the edges, underneath a wooden medicine bottle crate in a Shamrock antiques store last summer. A couple months after buying it, he took a closer look as he prepared to sell it on eBay.

He noticed there were several sheets with letterheads hinting at its past, like a page from a prescription pad from a Waco store titled "W.B. Morrison & Co. Old Corner Drug Store." An Internet search revealed Dr Pepper, first served in 1885, was invented at the Old Corner Drug Store in Waco by a pharmacist named Charles Alderton. Wade Morrison was a store owner.

Faded letters on the book's fraying brown cover say "Castles Formulas." John Castles was a partner of Morrison's for a time and was a druggist at that location as early as 1880, said Mary Beth Webster, collections manager at the Dr Pepper Museum and Free Enterprise Institute in Waco.

As he gathered more information, Waters took a slower turn through the pages filled with formulas for everything from piano polish to a hair restorer to a cough syrup. He eventually spotted the "D Peppers Pepsin Bitters" formula.

"It took three or four days before I actually realized what I had there," Waters said.

The recipe written in cursive in the ledger book is hard to make out, but ingredients seem to include mandrake root, sweet flag root and syrup.

Michael Riley, chief cataloger and historian for Heritage Auction Galleries, said they think it's an early recipe for Dr Pepper.

"We just feel like it's the earliest version of it," he said.