Letter 2 of 4 of Letters Miscellany, a collection of letters representing both sides of the calendar controversy. Letter 2, of which only one folio …
And his third argument, in which he
said ‘641
on its day, 642 the next day’, has no root in the words of the Sages, and even
the one who originally contrived this (argument)
and wrote it did not know his right hand from his left regarding the secret
of the calendar, because he said that if Nisan is born
on Sunday, Tuesday, or Thursday and Tishri on Tuesday, Thursday, or
Sabbath until six hours, it is not postponed, (and if it is born) after six
hours,
it is postponed—and he did not notice that when Nisan is born on
Sunday, Tuesday, or Thursday before six hours,
the corresponding Tishri on Tuesday, Thursday or Sabbath will be after six
hours, because there are between them two (week)days,
four hours, [and] 438 parts, so that when Nisan is born at four hours of the
day, Tishri
will be born at eight hours 438 parts; and if we postpone Nisan because of
Tishri, this contradicts his rule
that Nisan before noon is not postponed; and if we do not postpone Tishri
because of Nisan,
this contradicts his rule that Tishri after noon is postponed.