Macintosh PowerBook Duo 250 (1993)
The PowerBook Duo is a line of small subnotebooks manufactured and sold by Apple Computer from 1992 until 1997 as a more compact companion to the PowerBook line. Improving upon the PowerBook 100's portability (its immediate predecessor and Apple's third smallest laptop), the Duo came in seven different models. They were the Duo 210, 230, 250, 270c, 280, 280c, and 2300c, with the 210 and 230 being the earliest, and 2300c being the final incarnation before the entire line was dropped in early 1997. Weighing in at a mere 4.1 pounds and slightly smaller at 10.9 in × 8.5 in (280 mm × 220 mm) than a sheet of paper, only 1.4" thick, it was the lightest and smallest of all of Apple's PowerBooks of its time. Only the MacBook Air weighs less, though wider and deeper, but considerably thinner making it the second smallest subnotebook overall. The Duo had the most in common with the original MacBook Air which only included one USB 2.0 port, one video port (requiring an adapter) and one speaker port, but no ability for expansion. The PowerBook Duo line was replaced by the PowerBook 2400, which was slightly larger in size to the Duos, but still only the fifth smallest behind the 12 in (300 mm) PowerBook G4 which succeeded it as fourth smallest. Although both featured much more onboard functionality, they lacked docking ability. As of 2014, the subnotebook Apple offers is the MacBook Air.
via Wikipedia: http://en.wikipedia.org/wiki/PowerBook_Duo