It will probably not be a big chiddush to anyone reading this that eggs didn’t halve in size. What many people, including myself until recently, however, do not sufficiently appreciate is that the textual arguments for doubling of volume shiurim in the modern era are actually very strong, indeed, from a certain perspective, irrefutable. What is also underappreciated is that apologetic arguments made by defenders of the premodern shiurim are weak and belied by archaeological evidence. So I set out to find out what’s up, and I’m pretty sure I did, but, like I say, you probably won’t much like it. Anyway, here it is.
Rav Shlomo Zalman Auerbach brought the Gemara Shabbos 14a, which states that Chazal decreed that someone who drinks a reviit of impure liquid is considered impure because he might have a reviit of impure liquid in his mouth and then put some terumah in his mouth. It is practically impossible to hold 150ml of liquid in ones mouth and then add some food. A reviit cannot be so large.