Evolution of the 'shaku' unit of measurement

rematron · April 13, 2023

Hello all,

I read online that the modern shaku is 11.93 inches/30.3 cm but pre-1893 OR pre-1891 it was 13.96 inches/35.45 cm. There was no citation for this information in the article and I've been trying to confirm it somehow. Does anyone here know where I can read about this?

Thanks

Nobody · April 14, 2023

Ref. Shaku (unit) - Wikipedia

rematron · April 14, 2023

Thanks for trying @Nobody. I’ve already read that article and it does not address my question. It only states what the shaku equates to contemporarily.

rematron · April 14, 2023

“Traditionally, the actual length of the shakuvaried over time, location, and use. By the early 19th century, the shaku was largely within the range of 0.30175 to 0.303 meters (11.880 in to 11.929 in),[1] but a longer value of the shaku (also known as the kōrai-shaku) was also known, and was 1.17 times longer than the present value (35.5 centimeters or 14.0 inches).[7][2]”

The above is from the Wikipedia article. There is mention of the longer shaku, however, it does not confirm whether or not the “longer value” was considered the default value of the time or if it was one a a few varieties.

Bugyotsuji · April 14, 2023

You might find it interesting to read about the 笏Shaku, a symbol of authority throughout Asia, and Japan from the 6th century. Ivory for the upper ranks and wood for others. The standard length was, wait for it, I 尺shaku and 2 sun.

It is thought the name may be related to the length Shaku, though which came first may be a chicken-and-egg question.

Quote:

笏の長さが1尺であることから「シャク」になった。(=The length of a shaku was one shaku, which is why it came to be called a shaku.)

笏 - Wikipedia

A Tanto of over 30 cm was called a 寸伸短刀 Sun-nobi Tanto, or a tanto that is a　一寸 'sun' or two 'lengthened' or oversize.

Bugyotsuji · April 14, 2023

From Japanese Wiki, it seems that from the 5th century in Japan there was already a difference between the Korai (north Korean peninsula) shaku and that from China. Although still not clear today, probably 26 cm?

日本には唐制が導入され、大宝元年（701年）の大宝律令で大尺・小尺を制定している。ただし異説もあり、日本には大宝令以前に高句麗から渡来した大尺より2寸長い高麗尺が普及していたので、これが大宝令の大尺とされ、唐の大尺が小尺にされたともいう。この説では、後に現れる曲尺1尺2寸の呉服尺は高麗尺に基づくものであるとする。また、新井宏は寺院等の実測分析から高麗尺ではなく0.268 mの尺が使用されていたという古韓尺説をとなえている。なお岩田重雄は、隋代に小尺となる尺が朝鮮において5世紀中頃には26 cm代に伸張し、その後約150年変化しないとし、それを新井宏が古韓尺と呼んでいると説く。唐の大尺は現在の曲尺で9.78寸（296.3 mm）であり、それ以来ほとんど変化していないことになる。

尺 - Wikipedia

SteveM · April 14, 2023

There were a lot of different values for "shaku". The Bakufu tried to clarify this in the 1700s by proclaiming the "kanejaku" as the standard. Up until that time, the measurements for "kanejaku" were not unified or standardized, so the government tried to standardize based on a shaku measuring stick in Kumano Shrine. This is 30.365 cms. This shaku has come to be called the "Kyōhōjaku" because of the era when it was determined. But there were other shaku in use, which is why its tough, if not impossible, to nail down an exact definition for shaku. Not everyone had a copy of this stick of wood from the Kumano shrine with which to make their own "shaku" measuring tapes.

Here is a picture showing the various shaku. Top one is the Kyōhōjaku, middle one is the Matashirōjaku (～30cms, used by carpenters since 1504), and on the bottom is the Secchūjaku (30.297cms, a compromise between the above two shaku units, developed in 1800s by Inō Tadataka). The Secchūjaku was adopted by the Meiji goverment as the last "official" shaku measurement when they began converting to the metric system. So one Secchūjaku equals nearly 30.3 cms.

https://www.kahaku.go.jp/exhibitions/vm/past_parmanent/rikou/weights_and_measures/ruler.html

But even these three would be unknown to most farmers or townspeople, who probably used whatever "shaku" stick they had been passed down from their fathers. Cloth-sellers used a completely different shaku measurement (gofuku shaku) of about 36cm.

Putting links for reference

https://kotobank.jp/word/享保尺-245741#:~:text=〘名〙享保年間（,尺として統一したもの。

https://kotobank.jp/word/折衷尺-308379#:~:text=〘名〙江戸時代の物,も標準とされた。

https://nikido69.sakura.ne.jp/column/doryoukou/doryoukou01a.htm

SteveM · April 14, 2023

A summary in English that may be useful.

https://www.japanesewiki.com/history/Shaku (a unit of length defined by the traditional East Asian system of weights and measures).html

rematron · April 14, 2023

This is great. Thank you very much, @SteveM.

Bugyotsuji · April 14, 2023

We already have one shaku+/- for tanto, less than two shaku for wakizashi and two+ for katana. Useful division.

For me there is also a magic crossover point for rule-of-thumb measuring.

One shaku is about one foot, so one shaku is all of 10 sun, 30 cm and 12 inches, as close as dammit.

Actually these all fall within half a cm of each other. 30 cm is very slightly short of 10 sun, and 12 inches are very slightly longer than 10 sun.

To show how they regarded the similarity, one sun is 寸 and one inch is 吋, the addition of the mouth indicating a Western short 'sun'?

I have a battered but very useful pre-war tape measure which shows all three systems.

Mikaveli · April 15, 2023

31 minutes ago, Bugyotsuji said:

One shaku is about one foot, so one shaku is all of 10 sun, 30 cm and 12 inches, as close as dammit.

Actually these all fall within half a cm of each other. 30 cm is very slightly short of 10 sun, and 12 inches are very slightly longer than 10 sun

It seems we have anthropometry to thank for both the variance of the measures and their similarity.

Similar to the ft, the length of forearms, feet, hand span and thumb width seems common base units across cultures (the Roman foot is similar too).

Interestingly, both the ft and the shaku have varied over time, and in different contexts. I'm sure Markus Sesko wrote about the latter when researching Masamune blades.

Larason2 · April 15, 2023

As mentioned, the Japanese shaku (尺) is very similar to the Chinese chi, and has the same symbol (尺). Both are a unit of measurement of similar length, but both varied a lot in actual measurements all over China and Japan (and also all over Asia). As also mentioned, these units are also similar to the units used in the mediterranean from the same time period, including the Roman foot and the Minoan foot. The Minoans also had a symbol in Linear A that looks very similar to the asian symbols, but is reversed, which is hypothesized to also be a unit of measurement (*301). There are also some Linear A characters that are very similar to many ancient Chinese measure words (like “jin” 斤 *131b, “pian,” 片 *131c, and “ge” 个 *304.). Could be a coincidence, but could be a result of trade across the Egyptian canal that opened up in the Bronze age. As also mentioned, all of these measurements are about the length of a forearm.

Ken-Hawaii · April 15, 2023

Choose any unit of measure, & there's a long history of how it came to be chosen. A few of them actually make sense, like light-year...as long as you have the underlying technology.