By looks alone I would guess maple. In my experience though maple is fairly hard and heavy so with it being light weight it could be something else. It’s 90 years old though so it could just be very very dry. I’ve never seen poplar without a darkness or green hue to it so I wouldn’t suspect that. I have never heard of cedar elm that was mentioned above. If you know any real old farmers or carpenters that work on those old barns they wouldn’t probably have a better guess