I saw years ago a fascinating idea regarding the counting of sefiras haomer.
The source was discussing the change in counting between the days and the weeks.
We first start counting in base-10: "Today is 15 days"
and then, by counting in relation to the weeks, we effectively switch to base-7: "...which is 2 weeks and one day of the omer." (Sefardim mention the omer between the days and the weeks, but the concept is still the same.)
I remember the book (it was an English sefer) was discussing the concept of going from 10 to 7; I think it had something to do with the sefiros, which we sometimes count as 7 and sometimes as 10 (depending if you count chochma bina and daas/keser or not).
Does anyone know:
1) the English sefer which discusses this?
2) an earlier source for this concept, presumably from where the sefer was coming? (maharal, rav tzadok, etc.)
3) What is the concept of this transition from 10 to 7, and why is it significant specifically when discussing sefiras haomer? I've tried working it out but I don't have any clear explanation.
but I didn't find any discussion specifically about the sefiros transitioning between base-10 and base-7.