This paper presents an empirical evaluation of mouse-based interaction in seated Virtual Reality (VR) scenarios as an alternative to traditional VR controllers. We introduce Scaled Mouse, an interaction technique that shows the position of the real mouse in VR and maps standard mouse actions to 3D object manipulation using velocity-based scaling. We present two user studies assessing this method. In the first study, we compared a VR controller against our mouse-based method for manipulation tasks. Results show that the mouse consistently achieved higher rotation accuracy in 3D rotation and docking tasks than the controller, while maintaining comparable task completion times. Building on prior scaled interaction techniques, our second study investigated mouse interaction in a productivity-oriented scenario where users could combine 3D manipulation with a 2D adjustment panel. Scaled Mouse interaction was significantly faster and more accurate than the controller for 3D docking tasks and was rated significantly higher in usability and workload measures. Together, these findings establish the mouse as a viable and effective input device for seated VR contexts, offering both familiarity and accuracy advantages over controllers, particularly for professional and productivity-focused applications.