Yeah, I was going to say the force of gravity...but, switched it...still, I wasn't quick enough or smart enough to count on you...you found me out quickly enough....(this is an honest scale, but it has a huge plate and runs up slowly....I weigh more than 100 lbs....lol)
Not to be picky, but Gravity is a force. Now, when you set something on the scale, it compresses the (non existent) springs, which can be kinetic energy when they move, and then stored potential energy when they are fully compressed. With no springs, but perhaps a set of curved plates, the curved plates then carry the energy.
Now, that said, this is an interesting photo. The reflection adds a sense of place. I also like how you got a pretty precise weight of 100 lbs
