I know that there is a Gemarah (somewhere in Shabbos I think), that discuses birth signs, based on days of the week and month. The Gemarah ends with Ein Mazal B'Yisroel and a few stories that ...
There is an argument how many walls does a Rshus Harabim need to have to make it a Rshus Hayachid (Deoraisa). R' Yehuda says that one needs two walls, while the Chachamim said one needs three. The ...