Curtain mystery solved

The question is, in the era before computers how in the world did the artist come up with a complex repeating pattern that has no obvious joins on all four sides?

The only thing I can think of is that the original canvas was first painted in a cylindrical format to make sure the tops and bottoms matched.

And then the canvas was unrolled and formed into cylinder by joining the two sides followed by a re-working the edges so they matched as well.

Then the thing was then laid flat and used to make screen prints which were then printed onto the fabric with perfect edge matching on all four sides.