With Dan Brown's The Lost Symbol flying off bookstore shelves, we got to thinking about lesser known symbols, those that are usually recognized only within specific disciplines or have been lost to the ages. Famed industrial designer (and symbol junkie) Henry Dreyfuss and his staff once assembled a database of 20,000 symbols that served as raw material for the Symbol Sourcebook. Originally published in 1972 and now available from Wiley, the book still lives up to its subtitle—"An Authoritative Guide to International Graphic Symbols"—and comes complete with a wacky foreword by Buckminster Fuller. By focusing on "functional, instructive graphic symbols" and omitting alphabets, numbers, emblems, and logos, Dreyfuss created a visual reference that remains valuable and inspirational to designers—or anyone who might be curious about the universal symbol for everything from apricots to zeppelins.

We asked design historian Russell Flinchum, author of the authoritative biography of Dreyfuss, to shed some light on the Symbol Sourcebook. "The origins began with a desire to label John Deere and National Supply Co. (oil drilling equipment) with standard international labels that wouldn't have to be changed from country to country, thus saving much time and effort," he explained. The symbol gathering was primarily a joint project of Dreyfuss and hiw wife, Doris, who worked closely with Paul Clifton, the main designer on the project. "It began with a mass mailing of every organization involved with symbols they could think of, then collating this information and boiling it down to standard appearances." Dreyfuss used the same approach in preparing The Measure of Man, the pioneering ergonomic reference manual published in 1960.

"Nobody in the industrial design profession was really doing anything in these areas in the mid-1950s other than Dreyfuss, and I consider this to be his greatest contribution, more so than any of the individual designs," said Flinchum. "He gave away huge amounts of proprietary information for the modest cost of the publications" in what was "essentially a gift to the profession."

As for sentimental symbol favorites, Flinchum points to the page of Hobo symbols, used to signal everything from poor-quality drinking water to an easy mark (a series of slim triangles scratched on or near a dwelling was a recommendation to "tell a pitiful story" to the sympathetic ears inside). He describes their inclusion in the book, alongside the visual languages of engineering and metereology, as "a detail that I think of as very Henry, very human-centric...a language that Dreyfuss didn't want to see disappear."