Quantum spin liquids are exotic states of magnetic matter in which conventional magnetic ordering is suppressed. Magnetic analogues of ice are good candidates to observe this behaviour, but introducing quantum fluctuations has often proved challenging. We propose to study Ho3Mg2Sb3O14, which is a rare candidate material for quantum-ice behaviour. Our previous neutron-scattering measurements showed that this system has a continuum of magnetic excitations at very low temperature (~0.1 K) - experimental evidence for quantum fluctuations. Our OSIRIS measurements have two key objectives. First, to measure the low-energy magnetic excitations of Ho3Mg2Sb3O14 with much-improved energy resolution, allowing fine details of the spectrum to be resolved. Second, to measure a magnetically-diluted sample to isolate the single-ion excitations, to facilitate detailed comparisons with theory.