Take for instance, reforms in weights and measures. Weights and measures which have been created through the centuries, and which are different in different countries, appear at first glance to have taken one or other form by chance and to be too complicated. But in reality they are always based on one definite principle.  In each separate class of things or material to be measured, a different divisor or multiplier is used, sometimes very complicated as in the English system of weights - 16 ounces to a pound, 14 pounds to a stone for comparatively small weights and for larger weights 28 pounds to a quarter, 112 pounds to a hundredweight, 20 hundredweight to a ton; or, for instance, a simple multiplier like 8 in the Russian measurement of grain which is never repeated in relation to anything else. This is a real psychological method created by life and experience because, thanks to different coefficients in different cases a man making mental calculations cannot confuse objects of different denominations nor (if the need arises) the measures of different countries, because each order of multiplier itself tells him what is being measured and with what measure…I am sure that the idea of a ‘logical’ measure and the metric system was born in the minds of teachers of arithmetic, because it is so much easier to divide by ten…But for all ordinary necessities of life, the metric system is far less practical than the old systems, and it weakens to a considerable degree a man’s ability to make simple mental calculations...