Emerging mixed reality (MR) technologies, such as Microsoft HoloLens, present many exciting opportunities to the heritage sector. For example, the development of immersive experiences within gallery, library, archive, and museum (GLAM) spaces. Previous work on virtual and augmented reality (AR/VR) in such spaces is often limited to meta-layers of information beyond traditional modes. However, the affordances of MR potentially offer new ways to design content beyond AR/VR that can engage users as performers upon the stage of historically resonant and artistically charged places. This work-in-progress paper examines the case of the Augmented Telegrapher under development at Porthcurno Museum. A pilot study with 30 participants examined how to situate the Augmented Telegrapher into the context of a multi-player game, with particular attention given to which interaction style is more suitable: the use of sensors and gestures to manipulate virtual objects, or a tangible user interface grounded by relevant physical objects. Experimentation reveals a statistically significant difference in time taken to complete a data entry task (d = 1.32, p < .01) and data entry errors (d = 1.24, p < .01). This highlights several challenges in the manipulation of virtual objects, most notably the difficulty of manipulating virtual objects using unnatural maps of artificial gestures to intentions. This work-in-progress paper briefly outlines future directions in response to these challenges, paving the way towards an interaction design blueprint for mixed-reality experiences in GLAM spaces.