Sentence:  The system I quoted ... was a full system: 486 PC 8megRAM 140HD, 2 DVI boards, 1 Ascension Bird <WSD>flying mouse</WSD> (6D mouse with 3 buttons, used for navigation and interaction), 1 VirtualResearch Headmounted display, 1 Logitech Sonic 6D tracker for headmount, Sense8 software and environment. 
Meaning of the word marked with <WSD> tags:  An input device like a mouse that can be lifted from a surface and moved in three dimensions.