On the Wikipedia article for Passacaglia, there is an excerpt of a piece by 17th-century composer Bernardo Storace. It has a 6-line staff with both G and C clefs above a 7 line staff with both C and F clefs.
It seems obvious how to read this, but I had never encountered it before. Was it something that saw frequent use in the era?
One answer mentioned a connection to the harpsichord, and it seems plausible— could it be that the staves are expanded to match the ranges of the upper and lower manual on a 2-manual instrument?
However, another part of this score suggests that it might just be a way to write for four parts on two staves that is more readily accessible to musicians accustomed to reading soprano and tenor clef:
