Answer: 10 Tons of Potatoes

When Boeing needed to test Wi-Fi signal distribution within their airplane cabins, they opted to skip building expensive test dummies or hiring human subjects to sit in the seats.

Instead they went with a thoroughly low-tech approach: they filled the seats with large piles of potatoes. The dense, moist, and starchy mass of the potatoes absorbed the Wi-Fi signals in a fashion very similar to human test subjects, allowing them to test multiple antenna designs before trying out the final layouts with actual humans in the seats.