Unfortunately, the authors were somewhat arbitrary in deciding which units any particular one would be converted to. If I had written this book, I would have included at least the following for each unit: (1) All other units in the SAME system (i. e., if we are talking about a pre-revolutionary French unit of length, all other pre-revolutionary French units of length) and (2) the nearest-sized SI unit. Unfortunately they frequently leave out conversions between units of the same system that would be useful, and often units of the same approximate size are converted to different SI units, making comparisons difficult. (For example, one foot-size unit may be expressed as so many centimeters, while another as such a fraction of a meter.)

Both of these omissions can be circumvented by using a calculator and working with what these authors have chosen to include, but the book would be easier to use if they had done what I would have.