Fuel Dipsticks
After a lifetime, well at least since age 17, in aviation I have always used a visual check of tank contents where possible, or a known uplift of fuel plus indicated fuel remaining prior to refuel, to determine fuel on board for flight.
Anyone who gets airborne without ensuring there is sufficient fuel aboard for the intended flight is not only being negligent but also very foolish. The pilot in the incident cited by Centaurus obviously did not visually check the fuel in tanks on the Cessna and, I would suggest, was very fortunate to have recovered sufficient fuel to conduct the turn-back.