Tom Van Baak in LeapSecond.com:
In September 2005 (for the 50th anniversary of the atomic clock and 100th anniversary of the theory of relativity) we took several cesium clocks on a road trip to Mt Rainier; a family science experiment unlike anything you've seen before.
By keeping the clocks at altitude for a weekend we were able to detect and measure the effects of relativistic time dilation compared to atomic clocks we left at home. The amazing thing is that the experiment worked! The predicted and measured effect was just over 20 nanoseconds.
Dad makes final connections to the clocks. It took about half an hour to bring all the equipment down from the upstairs lab out to the car. The kids took the back seat.
Here's a view of the car. What a mess. The three clocks fit on a middle seat in the van. The front seat area is where I put the counters, laptop, inverters, power monitors, environmental sensors. It comes to 400 pounds of batteries; 200 pounds of clocks.