... The Square illumines with the light of reason to test our understanding found in the VSL. The Compass delineates the limits on our examination, illuminating the dark corners that may escape our notice.
Don't know who chose them but... the Universe is usually thought of as being a sphere and then we have the four corners of the Earth. Both the sphere and the cube are 'containers'.
The changing positions of the the tools might indicate that, as Shakespear wrote "There are more things IN heaven and earth, Horatio, Than are dreamt of in your philosophy".
(The level and the plumbrule on the other hand could be seen as indicators of directional flows, both have a beginning and an end but can't contain things.
Our birth is but a sleep and a forgetting…trailing clouds of glory do we come from God, who is our home -Wordsworth
The other way around ... yes, now you have bought it to my attention. As above so below etc etc.
I think of the Universe as a sphere - The Tzimtzum (Hebrew צמצום ṣimṣūm "contraction/constriction/condensation/withdrawal") is a term used in the Lurianic Kabbalah teaching of Isaac Luria, to explain his new doctrine that God began the process of creation by "contracting" his infinite light in order to allow for a "conceptual space" in which finite and seemingly independent realms could exist.
I just can't imagine someone inhaling a square space.
In Masonry there are four tassels attached to the corners of the pavement or the temple. But those are more likely to reflect four aspects of the galaxy veiled by four virtues.
One of the clues to the choice of Compasses is their placement so that the legs are to the West. (Some English-derived lodges have them the other way. That makes it much harder to discover their function in the lodge)
I posted this elsewhere but it may be of interest here:
The rays of Light (from the East and from the GAOTU) are symbolised by the compasses, and the square and the square pavement symbolise (are resonant with) the etheric grid of the temple that extends from E to W and N to S over the surface of the Earth.
From this we might assert that the Master is responsible for ensuring that the many Lights of Freemasonry find compatible anchorings in the square pavement and the square brethren.
As I have observed at several lodges, active rational thought tends to make the heads of brethren less receptive to the Light of the GAOTU as it descends from on high. When pointed out, those brethren have always become receptive to the flows then occurring.
There are also diagonal pavements that ought to be used when both Wardens are in the West e.g in some French workings, in the 18th and in the 30th. Those diagonal setups, when interacting with the Light from the East (but not the Light of the GAOTU) produce a different energy field, a bit further to the West than occurs with the Wardens at right angles.