code: public Quaterniond sub(double x, double y, double z, double w) {
          return new Quaterniond(this.x - x, this.y - y, this.z - z, this.w - w);
      }
docs: Subtracts the double components of another quaternion from this one.
  
  @param x The x (imaginary) component of the quaternion to subtract
  @param y The y (imaginary) component of the quaternion to subtract
  @param z The z (imaginary) component of the quaternion to subtract
  @param w The w (real) component of the quaternion to subtract
  @return A new quaternion, which is the difference of both