The first commercially sold portable was the 50-pound (23 kg) IBM 5100, introduced in 1975. The next major portables were Osborne's 24-pound (11 kg) CP/M-based Osborne 1 (1981) and Compaq's 28-pound (13 kg), advertised as 100% IBM PC compatible Compaq Portable (1983). These luggable computers still required a continuous connection to an external power source; this limitation was later overcome by the laptop.

Source: Wikipedia