I am getting closer to the end of this and I am running into the 8.8.3 "mathy numbers" rule that caused us some headaches during The Conquest of Bread again. Unsurprisingly given the subject matter, this book has a lot of numbers too. I was trying to figure out a rule of thumb for when "a series of numbers is close together in a sentence" and I wanted to submit some examples.
"My income of one hundred thousand francs is as inviolable as the grisette’s daily wage of seventy-five centimes; her attic is no more sacred than my suite of apartments."
Would we want to convert one hundred thousand here? Possibly no, since "one hundred thousand francs" is parallel to "seventy-five centimes" in this sentence? There are other cases too where a large number is compared to a small one, and it seems to me that in such cases they could be considered "close together" for the purposes of this rule.
"It is evident, for instance, that if a piece of land which is worth today one thousand francs was worth only five centimes when it was usurped, we really lose only the value of five centimes. A square league of earth would be hardly sufficient to support a savage in distress; today it supplies one thousand persons with the means of existence. Nine hundred and ninety-nine parts of this land is the legitimate property of the possessors; only one-thousandth of the value has been usurped."
The first sentence here raises the same question as the previous passage. The last sentence here seems really tricky because ostensibly, it's describing a mathematical calculation and in any case "nine hundred and ninety-nine" could be converted to 999 under the rules. But what about the "one-thousandth"? Is that something you'd then change into a fraction with digits?
"If France (more powerful than Catherine II) should say to Mademoiselle Rachel, 'You must act for one hundred louis, or else spin cotton;' to M. Duprez, 'You must sing for two thousand four hundred francs, or else work in the vineyard,'—do you think that the actress Rachel, and the singer Duprez, would abandon the stage? If they did, they would be the first to repent it.
"Mademoiselle Rachel receives, they say, sixty thousand francs annually from the Comédie-Française. For a talent like hers, it is a slight fee. Why not one hundred thousand francs, two hundred thousand francs? Why not a civil list? What meanness! Are we really guilty of chaffering with an artist like Mademoiselle Rachel?"
Now we have a case where the parallelism between numbers is across sentences and even paragraphs: if we do want to respect parallelism with how numbers are spelled out, how far does that parallelism go?
The printed edition of the book has a fairly consistent style, spelling out the numbers in all cases except for two extremely large numbers (in the billions and trillions) and in three cases where it uses fractions (I had to break out MathML for this since two of the fractions had calculations inside of them). Because the print version already has a consistent style and there are so many large numbers in this book, I'd personally lobby to just leave the printed style in place and avoid having to editorially edit a huge portion of the book (this also would save all of us a lot of hand-wrangling like this about how to apply the mathy numbers rule like these examples show).