Quantum spin ice is a novel form of matter in which the spins remain dynamic even at absolute zero due to quantum fluctuations. The requirements on the single-ion wavefunction for quantum ice behaviour are quite stringent. We propose to determine the single-ion ground state in the candidate quantum ice compound Pr2Sn2O7. We will achieve this by measuring the complete crystal field excitation spectrum and using advanced modeling to fit the spectrum to a crystal field Hamiltonian. The measurement will be made on a powder sample with several different incident energies and temperatures.