A royal decree of 1845 then made the new system mandatory and exclusive, which would only come into force on 1 January 1850. In preparation for this event, books, pamphlets and illustrative tables were produced, aimed above all at the lower classes.
Thus, in view of the imminent entry into force of the decree abolishing the old Piedmontese measures and establishing the Metric Decimal System, Don Bosco published a small book of 80 pages for his apprentices: "The Metric Decimal System", a model of pedagogical intuition, simplicity and usefulness.
In fact, for years Don Bosco had been in contact with mostly poor young people who attended evening or Sunday classes or worked in shops and factories, but also with artisans and peasants. All of them would need to familiarise themselves with the new measures and so this booklet came out in May 1849.
