There are two trains of thought I guess about "portable" machines.
First, the original definition of "portable" means it's not in a cabinet, but still weighs the same as a full size 57 Chevy.
Second, the modern definition of "portable" means it's light as breeze and you can carry it around in your back pack or purse.
Several years ago I found our Free Westinghouse machine in thrift store. The store was across the street from the muffler shop that was working on my wife's truck. I found the machine and bought it, then carried it across the street to her truck. I about had a hernia before I got that thing to the truck. But, and this is very important to me, when I use that thing it does not move. The case it's in needs a new set of rubber feets so it doesn't scrape up the table, but that's a minor thing.
The Singer I mentioned above isn't near as light as the new plastic machines, but it's still too light to do much of anything. I tried to move it just a little bit and it about slid across the table.
I like the old machines.
Joe