One of the basic concepts in Chinese Metaphysics is Heaven, Earth and Man the meaning of which depends on the context. The three form an integral part in all situations and it is the Man part that makes it impossible to set up scientific tests.
We leave the term "human qi" as undefined and its existence originates from a living person. The Chinese way of saying is that qi is born at the heart. The "heart" here does not refer to the heart we know in human anatomy. It does not refer to an organ but it is not the mind. That is why we leave it as undefined. The existence of human qi is obvious observation. When a person walks in, we can feel the qi he brings in. Sometimes we feel the qi of joy, sometimes the qi of bitterness and sometimes we feel sha qi. Sometimes even in the virtual world of the internet we can feel the kind of qi from a person's writing. There is another Chinese saying, "The facial appearance is given birth by the heart 相由心生". This actually means that the heart gives birth to qi and the kind of qi will appear on one's face.
Since human qi originates from the heart, belief or disbelief of something will affect the outcome. Do not underestimate this human qi that comes from the heart. There are many case studies of a dying person prolongs his life because he wants very much to wait for someone to come to say goodbye.
This leads to the use of placebo effect. Medical doctors usually use positive words to tell the patients that they will get well because of the right medication. If the patient trusts him, the effect of the medication is more powerful. Some doctors after diagnosis tell the patient that he is not sick and therefore does not need prescription. The patient is told to do more excersice and eat healthy. Most people will leave the doctors office happily. However, there are people who need given some pills or even injection otherwise they always think they have not been cured. Some doctors in Hong Kong give the patient vitamin pills or even inject distilled water and the patient recovers in no time. If it helps the patient to get well, why not?
In practising Feng Shui, some practitioners tell their clients to put a three-legged toad (also called a money frog) to attract wealth. This definitely has nothing to do with Feng Shui just as providing vitamin pills or water injection is not medical practice. The thing is, some clients report that it works well. Some who do not believe in such things merely refuse to buy the toad. They may even tell the practitioner the toad is ugly. This may also lead to the practitioner losing business. Well, well, I myself would not recommend such things. However, I have no objection to such practice as long as there is no claim that this is a Feng Shui practice.
It is not nonsense.
It is not Feng Shui practice.
You can say that it is loosely related to Chinese Metaphysics because it is the qi from the heart that makes it work. Since there are better ways in Feng Shui practices, why bother to use this? But as long as it does no harm, why bother to condemn it?
Some unethical practitioners may be selling a three-legged toad for a very high price claiming he has "opened the light" for the toad and it is very powerful because of this. The term is "Kai Guang 開光". This is to be condemned.
Master Joseph Yu - http://fsrcenter.blogspot.com