The October 30th issue of Jinja Shinpō included an article about the annual reisai (grand matsuri) at Hiyoshi Jinja in Akishima City, Tokyo. This matsuri takes place on the 17th of September, and includes a mikoshi parade through the streets of the city in the afternoon. So far, so standard, but this matsuri also includes a less common element.
The previous night, a “sakaki mikoshi” is taken along the same route. The sakaki mikoshi is created by local residents from sakaki branches that they cut down themselves. The final sakaki mikoshi is about five metres tall, and weighs about 250 kilograms. On the 16th, it was taken to the jinja precincts, accompanied by traditional matsuri music, called “hayashi”. At 23:50, the ujiko gathered at a ritual platform set up in front of the sakaki mikoshi, and a matsuri was performed by the chief priest of the jinja, Revd Hashimoto, including purification, offerings, and a norito.
When it turned midnight, a taiko drum was struck to signal the start of the procession, and the sakaki mikoshi set off, carried by young men from the area shouting “eiya!”. They carried it along a 4 km route that led back to the jinja, and when they returned, they shook the mikoshi vigorously. Then they put it down, and at a signal from a flute all jumped on the mikoshi in an attempt to seize the “Mikokorotsutsu” (probably; the article does not give a reading for the kanji) that is fixed at the peak. Winning this is supposed to bring good fortune.
The route followed by the sakaki mikoshi is the same as that followed by the main mikoshi, called the “miya mikoshi”, which means the mikoshi from the jinja itself. The sakaki mikoshi is, it seems, not thought to carry the kami. Rather, it purifies the route along which the kami will pass.
The matsuri was designated an Intangible Folk Cultural Property by Tokyo Prefecture in 1975, and it looks like a survival of ancient Shinto practices: it happens at night, and the mikoshi uses tree branches. However, in this case the history of the matsuri is well documented, and we know that this is not what happened.
In 1767, the jinja rebuilt the sanctuaries and mikoshi to celebrate the jinja receiving an official title. The matsuri was first held in that year to mark the completion of the rebuilding, and a picture survives, showing a procession led by the sakaki mikoshi, with the hayashi musicians on a float behind it, and the miya mikoshi behind that. The practice of taking the sakaki mikoshi around by itself at night to purify the route began in 1864, and has been maintained ever since.
The matsuri does appear to draw on ancient elements of Shinto practice, but that was most likely a deliberate choice in the eighteenth and nineteenth centuries. (While what happened is documented, as far as I know the motivation is not, so the claim that it deliberately drew on ancient elements is no more than plausible speculation.) In this case, the documentation survives to let us know that the matsuri is not ancient, which should remind us to be cautious in cases when the documentation does not survive.