A very low mass cryogenic telescope of moderate size is needed for the Space IR Telescope Facility (SIRTF). We evaluated multiple concepts for the JPL's SIRTF precursor, the 0.85 m IR telescope technology testbed with an emphasis on simultaneously achieving excellent image quality, minimum mass, and design simplicity. We selected an all-beryllium approach over one employing either silicon carbide or fused quartz mirrors. Based upon recent advances in beryllium powder metallurgy, including techniques for the reduction of residual stress, we are demonstrating that the telescope when cooled to 5 kelvins is capable of simultaneously meeting both the 6.5-micrometers diffraction-limited image quality requirement and the 30-kg mass goal. The design employs very few components and uses a single arch mirror to minimize telescope mass and simplify cryogenic mirror design, analysis, and testing. The telescope's inherently stiff metering tower combines the functions of secondary mirror support and stray light baffling. We describe the design and the trades by which we arrived at a final configuration.