Who compared the Trinity to a triangle with three right angles?

[Nicholas of Cusa](http://en.wikipedia.org/wiki/Nicholas_of_Cusa) (1401-1464), wrote in part 1, chapter 12 of his *De docta ignorantia* (1440): > Others who are very talented compared, to the Super-blessed Trinity, a triangle consisting of three equal right angles. 1 > *Alii peritissimi Trinitati superbenedictae triangulum trium aequalium et rectorum angulorum compararunt*. I think we are all aware of representations of the Trinity using an equilateral plane triangle. The triangle described by Nicholas is not possible in the plane, though it makes sense on the surface of a sphere, for example. He seems to imagine it (see ch. 19) as a planar figure having three infinite sides, and argues that the angles must necessarily be equal and as large as possible. 2 Setting aside any mathematical problems with his geometry, I'm curious about the origin of this image. It would seem to be related to other geometric metaphors for God, such as "an infinite line" or "a circle whose centre is everywhere and whose circumference is nowhere". But I have not heard this one before. **Who came up with this idea and what did they mean by it?** (By the way, the "others" in the quotation above means "some people who are not [Anselm](http://en.wikipedia.org/wiki/Anselm_of_Canterbury) " in context. I thought he might be talking about himself, but I don't know if there is another, earlier work of his which contains this triangle image. It seems to crop up in *De venatione sapientiae* chapter 26, but he says in its preface that he is 61 years old, which would make it later than *De docta ignorantia*. It's still possible that he's attributing his own belief to some deliberately-unnamed expert, but if so then I'd still like to find a definitive argument to that effect.) 1. Translation by Jasper Hopkins (1985) and appearing in his *Complete Philosophical and Theological Treatises of Nicholas of Cusa*, Arthur J. Banning Press, 2001. [Parallel texts from Cusanus-Portal](http://www.cusanus-portal.de/content/fw.php?werk=13&fw=34&ln=hopkins) .
2. It's not clear why he thinks they must be right angles. In some sense it would be more consistent with his reasoning for them all to be 180 degrees, which is one reason to believe that in this case, he's talking about someone else's idea.