@SergeStinckwich The QuaternionExtensions package has not been deleted from the file system yet. Initially, I unloaded the said package from Pharo and the tests still passed. This would indicate that we can safely delete it.

You have to modify the BaselineOfPolyMath that load the packages.

Presumeably I just remove L60 of that file: https://github.com/PolyMathOrg/PolyMath/blob/master/src/BaselineOfPolyMath/BaselineOfPolyMath.class.st

is that right?

No enough, replace two lines :

package: 'Math-Quaternion' with: [ spec requires: #('Math-Complex') ];
package: 'Math-QuaternionExtensions' with: [ spec requires: #('Math-DHB-Numerical' 'Math-Quaternion' 'Math-Polynomials') ];

with

package: 'Math-Quaternion' with: [ spec requires: #('Math-Complex' 'Math-DHB-Numerical' 'Math-Polynomials') ];

ok I merge your changes on master. Next time you should do a PR on development branch. Look at the contributing guide here: https://github.com/PolyMathOrg/PolyMath/blob/development/CONTRIBUTING.md