How to reset a configurable joint quaternion?

I need to reset (0,0,0,0) the value of a quaternion in a ConfigurableJoint.targetRotation.

I tried this: JointSchulter.GetComponent(ConfigurableJoint).targetRotation.Quaternion.Set(0.0, 0.0, 0.0, 0.0);

and this:

JointSchulter.GetComponent(ConfigurableJoint).targetRotation = Quaternion.Set(0.0, 0.0, 0.0, 0.0);

and this:

JointSchulter.GetComponent(ConfigurableJoint).targetRotation = Quaternion.Inverse(transform.localRotation);

None of them worked :-)