"If it doesn't fit in your pocket, you don't take it to dinner with you," says Jha.
And if you don't take it to dinner, a portable's usefulness and potential for volume production are diminished.
That suggests to me the Apple tablet being announced next Wednesday, won't be much more than 7" x 5".
Because that's what fits in my pocket.
Moreover the glass in a portable's display can't be much bigger than 6" to be strong enough.
Furthermore the Kindle, Amazon's book reader, only has a 6" display and many people read books on it.
So next week's Apple Tablet should be around 7" x 5" and do everything an iPhone can do as well as display books, newspapers and magazine articles effectively.
Well that's what I think.
By this time next week plus about four hours (10am Pacific Time/7pm GMT) you'll know how wrong I am.