Palatino 766 pipes, pools, cliffs, streams... (by Taccola)

[Koen G]

Is that an example of allegorical interpretation, if the VMs artist 'mistakes' the illustration of an aqueduct for a rainbow? Or repurposes it??

The point I'm trying to make is that no single source explains what we see in Q13. It's completely novel. But it's not devoid of influences, and this must have been one of them.

But you make a good point, in the sense that many of the added elements lean towards the less tangible, so to say. That's why I would still object to the view that the VM "hides" all kind of machinations on purpose.

The only conclusion I'd draw so far is that the VM makers must have had access to a book like this, or this very book. And they employed it in their project, whatever that may have been. 

Do we really have issues with artists, good or bad, drawing materials from more than one source?