Edward Sylvestre Morse, Japan day by day, vol. 2, Boston, Houghton Mufflin, pp. 223-224, 1917.

When we came away we were given a little souvenir of Suo, consisting of a thin wooden box about four inchees long lined with gold paper, across which was a narrow strip of black cloth on which were pasted seven caddis worm-cases (fig. 623)! These common objets in our streams are found in the river at Iwakuni. On the outside was a picture of the wonderful woden arched bridge, with a curious formula of trusses.