Some context for the symbolism that I think is missing from the article.
The person in the engraving is seen leaving a sphere containing an Earthly world. The term for this sphere is mentioned in the second sentence of the article, «firmament»: "passed his nights beneath a firmament shot through with stars". This word comes from common Bible translations describing the creation in Genesis as a firm object in Latin, στερέωμα (solid object) in Greek. https://en.wikipedia.org/wiki/Firmament
The circle in a circle in the sky as the article says is from the visions of Ezekiel where he claims he saw God upon a chariot which spawned a bunch of religious mysticism works called Merkabah (i.e. chariot) mysticism that lasted for some centuries. The chariot in the vision is said to be surrounded by different kind of angels, and one of them is the one that looks like a wheel inside a wheel. https://en.wikipedia.org/wiki/Merkabah_mysticism
The person in the engraving is seen leaving a sphere containing an Earthly world. The term for this sphere is mentioned in the second sentence of the article, «firmament»: "passed his nights beneath a firmament shot through with stars". This word comes from common Bible translations describing the creation in Genesis as a firm object in Latin, στερέωμα (solid object) in Greek. https://en.wikipedia.org/wiki/Firmament
The circle in a circle in the sky as the article says is from the visions of Ezekiel where he claims he saw God upon a chariot which spawned a bunch of religious mysticism works called Merkabah (i.e. chariot) mysticism that lasted for some centuries. The chariot in the vision is said to be surrounded by different kind of angels, and one of them is the one that looks like a wheel inside a wheel. https://en.wikipedia.org/wiki/Merkabah_mysticism