2 occurrences across the corpus

OT Pseudepigrapha

The Letter of Aristeas 3:22

Now the upper edge of the two sides, being elevated, was sharp since, as we have said, the rim was three-sided, from whatever point of view one approached it.

Kebra Nagast

Kebra Nagast 100:55

And God said unto him, "Make thyself a four-sided ark, and build it with the work of the carpenter, and make for it three storeys inside, and go into it with all thy house."