bsfeechannel: we are taught all of this in school. Every American since 1970's was taught in metric and has learned all these tricks and knows of every single textbook advantage of metric. If this is you caring about Americans, then thanks for the concern. We will feel your prayers.
But if you're in Disneyland, and the map is in Mickey Miles, what's wrong with using Mickey Miles? If you are completely aware of the benefits you are theoretically giving up, determine that none of them really applies to your daily life, and you have no problem using metric if and when you want (and how you want, using fractions with metric and/or metricizing imperial by sticking with a single base unit for an entire calculation no matter how big the numbers get) then what's the problem, really? Esp now that we have calculators and smart phones? (And zeros and scientific notation).
Your compatriots' ideas about saving money have all been addressed, already. You keep coming back to that idea without bringing anything new. If you disagree with either of these statements, then go ahead and refresh my memory. I would appreciate that.
;;
A sextarius measured in modern inches is about 589.934304 mL, which is 19.94805194805 modern oz.
Using wikipedia's best guess of a Roman inch as 0.9708 modern inches, makes it 539.7503761 mL, or 18.251131470774 modern oz.
So maybe I was wrong about the wine bottle. This sounds more like a British pint of beer. Adjusted for
average BMI. And ~18 fl oz is a pretty common size of a draft beer in America. Well, it can be anything from little as ~12-13 oz at a ball game and up to 22 oz, depending on how close you get to a university.
A sextarius based on the modern gallon would be 21 1/3 fl oz. So the "American sextarius" is a Colt 45. 22oz of malt liquor. Sometimes called a "double deuce" by high school kids and homeless people. Fits a brown paper bag just right. This BMI thing is hitting too close to home, now. I prefer to calculate it the Roman way, to make it 19.95 oz, or a Brit pint.
The other interesting thing about the sextarius is it's 36 cubic inches. This is easily divisible a lot of ways without ending up with fractions. Notably, it is divisible by 12, which the Sumerians seemed to like. If you divided a congius into 8ths, you get 27 cubic inches. Going the other way, there are 48 sextaria in a cubic foot, and 48 is divisible by 12; 64 is not. Perhaps the Sumerians found it useful to have these divisible by 12 type of units, because they were proficient traders. Dealing with high volumes of things carried on camels and boats, they may have liked to carry and to trade for the correct number of identically packaged goods in order to bundle or stow them, efficiently, and/or to visually estimate the amount of stuff they can get into the boat. And perhaps multiples of 12 happen to be particularly flexible and efficient in some aspects of the real world logistics of packaging/storing things. Like soda comes in 6 packs, 12 packs, 24 packs. No 5 or 7 packs. Like your metric butter is sold in 1/4 kilo's. Because 4 sticks fit in a box. But apply that to pallets of goods being loaded at the dock.
Dividing the 1/8th cubic foot into 8ths also ends up with only 13.7 oz, using Roman inches. 14.96 using modern inches. That's a bit shy of a proper draft, even in America.
This gallon vs congius disparity is evidence that mankind may have temporarily forgotten that the gallon and the inch were related, sometime back. I blame the Brits for this. They were living in straw huts covered in dung when the Romans arrived to mine their gold. And they went back to living in mud huts after the gold ran out and the Romans left. But those brits possibly developed an appreciation for and an uncanny calibration to the size of a Roman beer.
Come to think of it, one of the first things I read in my 20 seconds of google research was Sumerians liked their beer. To a less advanced society, buying and drinking imported Sumerian or Roman beer would have been a curiosity. And the containers would have been way more consistently produced than anything they had seen in their lives. Some of the empty bottles may have lived on as measuring tools. Beer. We have inches because beer.
Ah, hmm? wikipedia: Pint comes from the Old French word pinte and perhaps ultimately from Vulgar Latin pincta meaning "painted", for marks painted on the side of a container to show capacity.