Pīti and sukha for first jhāna simile from Vism.: man in desert sees water, gets pīti. drinks water, gets sukha.

 

♦ 73. itaraṃ pana sukhanaṃ sukhaṃ, 

suṭṭhu vā khādati, 

khanati ca kāyacittābādhanti sukhaṃ, 

taṃ sātalakkhaṇaṃ, 

sampayuttānaṃ upabrūhanarasaṃ, anuggahapaccupaṭṭhānaṃ. 

satipi ca nesaṃ katthaci avippayoge iṭṭhārammaṇapaṭilābhatuṭṭhi pīti. paṭiladdharasānubhavanaṃ sukhaṃ. yattha pīti, tattha sukhaṃ. yattha sukhaṃ, tattha na niyamato pīti. saṅkhārakkhandhasaṅgahitā pīti. vedanākkhandhasaṅgahitaṃ sukhaṃ. kantārakhinnassa vanantudakadassanasavanesu viya pīti. vanacchāyāpavesanaudakaparibhogesu viya sukhaṃ. tasmiṃ tasmiṃ samaye pākaṭabhāvato cetaṃ vuttanti veditabbaṃ. iti ayañca pīti idañca sukhaṃ assa jhānassa, asmiṃ vā jhāne atthīti idaṃ jhānaṃ pītisukhanti vuccati.

100. But as to the other word: pleasing (sukhana) is bliss (sukha). 

Or alternatively: it thoroughly (SUṭṭhu) devours (KHĀdati), 

consumes (KHAṇati),30 bodily and mental affliction, thus it is bliss (sukha). 

It has gratifying as its characteristic. 

Its function is to intensify associated states. It is manifested as aid.

And wherever the two are associated, happiness is the contentedness at getting a desirable object, and bliss is the actual experiencing of it when got. Where there is happiness there is bliss (pleasure); but where there is bliss there is not necessarily happiness. Happiness (piti) is included in the formations aggregate; bliss (sukha) is included in the feeling aggregate. If a man, exhausted31 in a desert, saw or heard about a pond on the edge of a wood, he would have happiness (pīti); if he went into the wood’s shade and used the water, he would have bliss (sukha). And it should be understood that this is said because they are obvious on such occasions.