# An example of Lieb's adiabatic process

I'm reading The Physics and Mathematics of the Second Law of Thermodynamics and have a question about the definition of the adiabatic accessibility.

It is defined as follows in page 16:

A state $$Y$$ is adiabatically accessible from a state $$X$$, in symbols $$X \prec Y$$, if it is possible to change the state from $$X$$ to $$Y$$ by means of an interaction with some device (which may consist of mechanical and electrical parts as well as auxiliary thermodynamic systems) and a weight, in such a way that the device returns to its initial state at the end of the process whereas the weight may have changed its position in a gravitational field.

Can you give me some examples of this kind of devices?