"Height" of seated statues in the medieval period

I wrote about the sculpture of Dainichi that was sold at Christie's for $14 million here and here. Concerning the sculpture, I recently noticed that an interesting discussion was going on at the bulletin board of the Japanese Medieval History Archives (in Japanese). The discussion was on an article in the International Herald Tribune. The IHT article was a detailed one that mentioned another sculpture of Dainichi, Kotokuji Dainichi, preserved in Ashikaga and that discussed which of the statues, the Kotokuji Dainichi and the one sold at the Christies, was the true sculpture that Ashikaga Yoshikane commissioned. The following is from the IHT article.

One well-known statue by Unkei, in particular, which is preserved in the town of Ashikaga in Tochigi Prefecture and is also a seated figure of Dainichi presents a distinct kinship to the newly "discovered" sculpture. Known as the Kotokuji Dainichi, Unkei's statue in Ashikaga has traditionally been assumed by Japanese scholars to be the statue which, according to a document of the later Muromachi period, was commissioned in 1193 by a Buddhist devotee from the town of Ashikaga, a certain Ashikaga Yoshikane.

Yamamoto Tsutomu, who had discussed Unkei's Kotokuji Dainichi in an essay on the Dainichi Nyorai, was gripped. When X-rayed, the newly discovered sculpture was shown to contain three dedicatory objects inside the hollow torso. These were a wood placard topped by a finial in the shape of a five-element pagoda, in turn containing a small rock crystal pagoda, and a rock crystal lotus bud mounted on a bronze lotus chalice pedestal. The five-element pagoda, Gorin-to in Japanese, literally "five-wheel pagoda," appeared in the late 12th century which contributed to circumscribe the period of the discovered sculpture. Most significantly, X-rays revealed that Unkei's Kotokuji Dainichi contained similar dedicatory objects.
The author seems to be a pundit of art. However, his argument get to be miserable when he become arrogant, as follows.
What truly excited Yamamoto was that the newly discovered sculpture fitted rather better the Muromachi period description of Unkei's Kotokuji Dainichi because its dimensions made it more plausible. It was 66 centimeters, or roughly two feet, high, while the piece in Ashikaga is only 32 centimeters high. True, the dimensions stated in the Muromachi period document, "three shaku," are understood by Japanese art historians to be equivalent to "three feet."

Whether wrong by two-thirds or just one-third, such loose evidence might perhaps be thrown out in a court of law. But to art historians who like to take the broad-minded approach, this is good enough. So, to quote Christie's very lengthy but very carefully worded entry, "Yamamoto concluded that the Muromachi document must point not to the Kotokuji statue but to this previously unknown masterwork."
According to a commenter at the bulletin board of the Japanese Medieval History Archives, it is commonsense among Japanese art historians that the size of Buddhism sculptures was described in documents in the medieval period as the height of the sculpture when it rose to its feet. As for seated figures, there was a commonly used method in the medieval period to convert the height of a seated figure into the true "height" of the statue. First, the distance from the bottom to the hairline on the neck was measured, then the distance was doubled. The doubled distance was regarded as the "height" of the statue. The distance from the bottom to the hairline was called hassaiko (髪際高). The hassaiko of the sculpture sold at Christie's was 45.5cm. Thus, its "height" (45.5 cm x 2 = 91 cm) is almost equal to "three shaku (= 90.9 cm)" described in the Muromachi period document. It is apparent that the sculpture was made as a seated figure of three-syaku Dainichi.

The author of the IHT article may have relatively rich knowledge about Japanese art, but not to the extent that he can make little of Japanese art historians.

This Webpage shows an article (in Japanese) of the Japanese art historian mentioned in the IHT article, Tsutomu Yamamoto, describing the details of the sculpture. Of course, the article mentioned the hassaiko of the sculpture that was used to calculate the "height" of seated statues in the Muromachi period.