Here's an example, I think the idea of chakras is "natural" in the sense given on the right. Chakras are "subtle energy" centres in the human body - the numbers vary, but in a basic 3-chakra sytem there is one in your guts (just below your navel, about 2 inches in), one in your chest and one in the centre of your head. The thing is, this does make subjective sense: we experience emotions as embodied, and this comes across clearly in language: "gut feeling", "open hearted" and so on. An instruction to "open your heart chakra" does kind of mean something - it relates to a sort of feeling, a sort of imaginative effort you can make which results in a change in physical feeling. Chakra-type notions seem to pop up cross-culturally and historically - for example Descarte's location of the soul in the pineal gland.
Now this does not imply that you really have psychic energies centres in the same sense that you have kidneys and neurotransmitters. If an alternative therapist "balances your chakras" something may very well have happened to you but it will be nothing beyond an increase in physiological relaxation. But I do suggest that the subjective experience of inner somatic spaces might be a universal one (one could argue that this means they are "real" in a sense, though I find that use of the word "real" unhelpful to say the least).
So chakra-believers are not 'deluded': they report an experience which they truly have. However, their thinking is scientifically unsophisticated (which is not to say it might not be emotionally sophisticated); intellectually, they should get out more.