Extract from the history section of the Nippon Culture mailing list:
http://www.yk.rim.or.jp/~planet/index.html
There was a song of a pack-horse driver saying,
"Difficult against one's wishes to cross the Ooi River,
while possible to go over the Hakone mountains on horseback."
"Hakone hachiri wa uma demo kosu ga,
Kosu ni kosarenu Ooi-gawa."
In the Edo period, it was permitted to travel rather freely around the country except passing through the
checkpoint of Hakone and crossing the Ooi River.
In those days, "Iri-teppou" and "De-onna" were especially marked by the Edo shogunate. "Iri-teppo" (In-guns?)
are guns which were brought into Edo from the western countries such as Satsuma-han or Choushu-han. "De-
onna" (Out-women ?) are such women as the ladies of daimyo or their maidservants who went out of Edo to
the western countries hidding confidentials away. The ladied of daimyo were compelled to stay in Edo as a kind
of hostages. The Edo shogunate was very nervous of the tendency of the western counries and paid close
attention to taking guns for rebelling against it into Edo and to leaking out secret information of the shogunate
through forge women travellers of the western daimyo.
The Ooi River waited for those travellers who successfully passed through the checkpoint of Hakone.
The shogunate intentionally didn't construct any bridge across the Ooi River in order to prevent the western
armies from advancing into Edo. The melting snow on the Mt. Fuji or heavy rains sometimes caused a sudden
rise in the River. At that time, travellers inevitably put up at inns in Mishima (in Shizuoka prefecture at present)
along the River.
In those days, as a post town, very prosperous was Mishima where there were many "geisha" who came from
Edo or other districts."
For your delectation - Tom