The misunderstanding seems to come from two sources in the suttas. The first one is in the description of the Seven Factors of Awakening that is found in the Ānāpānasati Sutta at MN 118. At verse 34 it says, "In one who is rapturous, the body and the mind become tranquil. On whatever occasion the body and the mind become tranquil in a bhikkhu who is rapturous – on that occasion the tranquility enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him." The conclusion is then made that pīti can't be referring to the physically energetic component of the first two jhānas because obviously that energetic component is incompatible with tranquility.

However they have missed the larger context such as is found in the chapter in Right Concentration on The Jhāna Summary and the Upanisā Sutta (SN 12.23). The same subpattern of tranquility following from pīti occurs in these larger patterns as well. As we saw in the chapter on The Jhāna Summary, the larger pattern in both of these is

pāmojja (gladness), pīti, pasaddhakāya (bodily tranquility), sukha, samādhi, (concentration)

gladness, emotional happiness, bodily tranquility, physical rapture, concentration.

The second source of confusion seems to be the description of the third jhāna where, after the pīti has faded and only the sukha remains, it says one "experiences happiness with the body." Those who think sukha is physical seem to assume this bodily happiness arises because of the presence of the sukha – entirely missing the point that the happiness with the body arises because the pīti has faded away. See the chapter in Right Concentration on on the 3rd Jhāna for a more complete discussion of this.

In the first two jhānas, both pīti and sukha are present and in the third only sukha is present. If we were to translate pīti as "emotional happiness" and sukha as "physical rapture," we would have emotional happiness and physical rapture in the first two jhānas and have only the physical rapture present in the third jhāna. But people who are trying to learn the jhānas sometimes, instead of generating an experience of both emotional happiness and physical rapture, wind up generating an experience of only emotional happiness and no physical rapture; others generate only physical rapture and no emotional happiness. Those with only emotional happiness and no physical rapture find the state quite nice and also workable for accessing the fourth jhāna. Those with only physical rapture and no emotional happiness find themselves in a state that is most unpleasant and completely unworkable for doing anything – yet that state would correspond to the third jhāna if pīti were emotional happiness and sukha were physical rapture. Clearly this is not the case.

Perhaps those who think sukha is physical may also be confused by thinking that the kāyena in the phrase sukha kāyena is solely referring to the physical body. But since kāya means "group, heap, collection;" it is probably referring to both the body and mind.

An additional source of misunderstanding seems to come from The Peṭakopadesa – Stories of the Hungry Ghosts, a text sometimes included in the Khuddaka Nikāya of the Pali Canon. Pīti there is defined as a mental quality and sukha, in the context of jhāna is defined as bodily pleasure. But this is a late text and certainly not a good source for understanding what is described in the suttas – and perhaps it is making the same two mistakes outlined above.

The similes for the first 3 jhānas also provide useful clues to the sutta understanding of pīti and sukha:

1st jhāna: bath attendant making soap – vigorous activity - lots of physical energy - pīti & sukha

2nd jhāna: spring in a lake – gentle activity - calmer with inner tranquility - pīti & sukha

3rd jhāna: lotus blossoms underwater – no activity - very still - sukha & no pīti

Even the very late Visuddhimagga indicates that pīti is physical and sukha is mental. It describes five grades of pīti such that there is certainly an indication of a physical component for pīti, especially in the fourth grade of "uplifting pīti" (even if you toss out the levitating!).1 And in describing the jhānas, the Visuddhimagga says "Pīti is included in the rūpa aggregate; sukha is included in the vedanā aggregate" (which is mental).2

In conclusion, pīti is physical; sukha is mental. Reversing this leads to nonsense and confusion, especially regarding the third jhāna and the similes for the first three jhānas.

1. Vsm IV.94-99, pp 137-139.
2. Vsm IV.100, p. 139.