Probably the earliest depiction of a communication device resembling a laptop has been discovered in an ancient Flash Gordon comics by Mende Petreski of Prilep, Macedonia.

Browsing through his comics collection, Mr. Petreski stumbled upon a panel in Politikin Zabavnik weekly published June 14, 1974, featuring the forces of Ming the Merciless using a device which looks a lot like a laptop to talk to their leader.

Science Fiction Observer: First “Laptop” Discovered in Flash Gordon Comics

(via Disinfo)