Information from A. S. Njoh (In Africa, Vol. 8 no. 4 of October 1935; 547-48.)
Witches are people believed to possess invisible powers, that nobody can explain, to do harm to others. This power is said to be in the heart of one so accused and it is not quite certain whether he knows of it himself. To prove that one is a witch or wizard the root of a certain herb (pwave) is mixed with water in a bowl and given to one to drink it. If he does not vomit he is said to be a witch, but if he does he is not a witch.
It is believed that the witches go about looking at all men in the town, and those they think will rise above them they try to find a way to quarrel with so that can destroy either them or their property
When the victim is ill, his relatives go to a native sorcerer who tells them to kill either a goat, sheep, dog, or chicken, or at time all. When this is done the sufferer recovers. Hence it is believed that the witches promise these animals before attacking one.
To guard oneself from witches one has to get either a bush apple (wizard's apple) or the bark of a special tree and hang it by the top of the door. It is also believed that witches do their harm at night. When a witch enters such an armed house to do harm to some one in it he will be opposed by the above and will die after a few days. But if one is a witch and aims not to harm any one in the house he will only be badly sick and when treated will be well. Here it ends.
In the Mokpe tradition, if someone is accused of witchcraft, that person is put through the Kwahwhe ordeal, also referred to as the Sasswood ordeal. That is, the person is made to drink a very bitter and noxious concoction made of several herbs and tree backs. The vile mixture is supposed to induce instant vomiting in the ordinary innocent person. Now, only witches and wizards are supposed to have the iron stomachs that can withstand the kwahwhe. Hence they do not vomit like ordinary persons. Innocent people are said to always vomit the Kwahwhe and hence pass the test.
In fact the "official" reason given by the Germans for their failed punitive expedition to Buea in 1891 was their outrage at the "barbaric injustice of the practice". An accused/alleged witch (Monjo Mw'Ikundi) was given the Kwahwhe. She was so frightened that her system shut down and she failed to vomit. She was found guilty and executed (hanged).
There is a Mopke proverb that states: E mbunga Kwahwe yoko szai (The dregs of the kwahwhe is the most bitter part). The English translation is the equivalent of : The darkest part of the day is the dawn.It is meant to encourage people to persevere because even the most unpleasant and painful experience will pass as surely as day follows night.