they even had a project for hydraulic-driven wheels - some kind-of water-mill in each wheel, and a huge pump, and that's it :)

p.s. long time ago i bought a 15y old hydraulic Citroen, drove it for 10 years.. the hydraulics was less breaking than the engine :/ . Now i have another (recent) Citroen but that "road-surface-ignorant" feeling of the hydraulics is completely gone.