Magnitude estimations were obtained for manual assessments of pure elastic stiffness stimuli (metal springs). 20 subjects of varied experience in manual assessment of spinal stiffness volunteered to participate. The mean exponent of the power function relating perceived magnitude of elastic stiffness to measured physical magnitude was 1.65. Exponents varied across the 20 individuals but were stable across testing sessions held at least 2 weeks apart, and the size of the exponent was not related to prior experience.