Psion/Sony/Toshiba/Olivetti NOT first
The Tandy 100: 1983; 4 pounds, 24 hours on 4 AA batteries.
The Poqet PC: 1989; 1 pound, 7.3" display, 100 hours on AA batteries.
My only computer since 2001 has been a two-pound Picturebook (8.9" 1024x480 display, hooked up to a 17" when at home); I'll be moving on to a Wind or eee, and sad to lose the Trackpoint and third mouse button.