Is it possible to compare approximately inertial frames in the inertial property? If this is the case, the inertial property becomes a measurable quantity. We give a positive answer to this question, and discuss the general principle of design of devices for making the required measurements. This paper is intended for advanced undergraduate and graduate students in high energy physics and relativity. Our aim is twofold: (i) to provide a deeper insight into the essentials of classical dynamics, and (ii) to give impetus to ingenious young people to devise new clever, useful and highly sensitive tools for measuring the inertial property following the pattern outlined in the present discussion. (Contains 3 figures and 3 footnotes.)