When we did it in high school (70's) we just used compound that had a long chain (soap?) and only one end dissolved in the water. It was very easy to measure and calculate the size of the molecule . We had a series of these simple experiments. Another I recall was measure the speed at which certain volatile compounds moved through the air.

I definitely learned that all science doesn't have to involve complex equipment.

The original way was to cover the surface of a round bowl with oil. It certainly makes a lot more sense to me than trying to measure a floating disk of oil.