Seidensticker again <stats query>

[Stephen Forrest <sforrest@husc.harvard.edu>]

Regarding John Erlandsson's note, I too just happened to be reading Tokyo 
Rising the other day when I noticed this:

"In 1960 both (Wakanohana and Tochinishiki) went into the fifteenth and 
last day of the March tournament undefeated.  It was the first time in the 
history of the sport that two Yokozuna had gone into the final day in 
that condition." (Wakanohana won).

My first question was, can this be true?  Any time you have two or more
yokozuna you might expect that there's a highish chance of a play-off for
the tournament between (two of) them on senshuuraku.  I guess that if
getting zensho is so difficult as it evidently is, the odds of both
yokozuna going even to 14-0 are not so high, but still... Was it really as
late as 1960 for this?  Has it happened (ever?lots?) since?  I don't have
much in the way of reference materials to check against, so if anyone
knows I'd be happy for some perspective on this.  Do you think there's
much likelihood of such a match in the Ake-Taka era (when Akebono starts 
listening to his dieticians, perhaps?)?
Meanwhile, back to building a banzuke.
Cheers,
	Steve Forrest