Still, his committee wondered, would the 160-character maximum be enough space to prove a useful form of communication? Having zero market research, they based their initial assumptions on two “convincing arguments,” Hillebrand said. For one, they found that postcards often contained fewer than 150 characters. Second, they analyzed a set of messages sent through Telex, a then-prevalent telegraphy network for business professionals. Despite not having a technical limitation, Hillebrand said, Telex transmissions were usually about the same length as postcards.
Source: Los Angeles Times