In the Preface to his Guiding Symptoms, Hering wrote
Many years ago, for the benefit of the students at Allentown, the following little scheme was written on the blackboard in the lectures on Materia Medica
As this represents the 4 principal Dimensions of a Complete Symptom introduced by Boenninghausen in his essay A Contribution to the Judgement Concerning The Characteristic Value of Symptoms and represented in the structure of his Therapeutic Pocketbook, I reference this as “the Boenninghausen X-diagram,” tho the graphic representation can be credited to Hering’s use in his Materia Medica lectures at the Allentown Academy.