In 1916, for the price of $100, you could purchase an aftermarket telescoping apartment to install on you model T Ford truck.
The side sections and the rear section expanded outward to give campers additional living space. When it was time to travel both of the side cabinets slide in and the rear section telescopes into the main compartment and is secured.
This was one of my favorite displays at the RV Museum & Hall of Fame in Elkhart, Indiana. If you like RVs and history you should plan an RV trip to the RV Museum.