In 2008 I inadvertently became aware of a very early example of a solar wheel toy. The NYTimes published a review of an art exhibit in NYC by the artist Jess. The article was illustrated with this photo of Jess' Crito’s Socrates: Translation #3 (1964), which looks eerily like a solar rocker. A bit of library research discovered Jess patterned his oil painting after an etching from an 1887 issue of Scientific American. The "thermoscopic balance" uses a principle similar to the drinking bird - basically, heat causes a low boiling point liquid to evaporate and force fluid from one chamber to the next, unbalancing the device. The second chamber is then exposed to the heat, while the first cools, and the cycle repeats.
There is an even earlier patent by A. and A. Iske whose operating principle is similar to the thermoscopic balance and easily understood from Fig 3 of US Patent 243,909 (the wheel is sitting in a warm liquid bath). Sadly, no patent model was submitted to support their 1881 invention.
There are also an old German clock called the "Puja" by Jauch and Schmid that uses the same principles for the motor.
Minto Wheel (1976), perhaps the best known thermoscopic motor, is really a flock of "drinking
bird" toys, arranged in a circle. Enjoy reading the article about the
Minto wheel, but be very skeptical about its "free energy" claims, and the purported
efficiency of the machine. Terry Tharp, for example, offers a calculation of the wheel's efficiency- (which is limited by thermal conduction), and finds it wanting.
And just for fun, try building this solar
variation of the rocker, based on modifying an actual drinking bird toy.