Inspired by https://www.thingiverse.com/thing:209132
I wanted to make a sphere in a cube.
But it is a bit hard to print so I made some adjustments to make it easier to print.
v1: simple wireframe cube containing a sphere with diameter equal to the cube side lentgh.
v2: rather use a diamond shape for the sides so the top frame is supported
v3: use a diamond shape for all sides, since it is easy enough to bridge (especially if you print up to 50% scale)
v4: add manual suports for the top frame and the spere.
I've had success printing up to 50% scale, 0.4 layer height, PLA and about 40% infill (to avoid the sides of the sphere to curl up on the bottom).