latin - Grammaticality: 'something than which nothing greater can be thought'

Source: pp 158-159, The Cambridge Companion to Anselm, by Brian Davies, Brian Leftow

What Anselm describes himself as looking for here he believed he had found when reflecting on the idea that God is "something than which nothing greater can be thought" (aliquid quo maius nihil cogitari potest).

The bolded looks wrong. How can something (a pronoun) precede than (a preposition)?
Why was the bold not written as: something OTHER than which?

Surprisingly, Google reveals no other context with this syntax (which I first encountered here)

PS: I reorder the first two sentences in the quote to facilitate understanding:

[Anselm] believed he had found
[w]hat Anselm describes himself as looking for here[,] when reflecting [...]

Answer

(This is actually similar to the two existing answers. I'd like to make the structure more obvious.)

The clause in the question should become obvious if we rewrite it as two clauses:

God is something than which nothing greater can be thought
= [ God is something ] + [ Nothing greater than (that thing) can be thought ]

_{(Also note that, as LePressentiment suggests below, God is something which nothing greater than can be thought would be another possible rewrite.)}

Another note: think being used transitively is common enough, e.g., We think the same. You think what? Think Green.