Dear Thomas,

> I have checked the text, but do not see any information you indicate
> here. Could you point out the sentences or the translation here
> please. Thank you.

In Maharahulovada sutta (MN 62) you can find two passages devoted to
'tejodhaatu'

“Katamaa ca, raahula, tejodhaatu? Tejodhaatu siyaa
ajjhattikaa, siyaa baahiraa. Katamaa ca, raahula, ajjhattikaa
tejodhaatu? Ya.m ajjhatta.m paccatta.m tejo tejogata.m upaadinna.m,
seyyathida.m– yena ca santappati yena ca jiiriiyati yena ca
pari.dayhati yena ca asitapiitakhaayitasaayita.m sammaa
pari.naama.m gacchati, ya.m vaa pana~n~nampi ki~nci ajjhatta.m
paccatta.m tejo tejogata.m upaadinna.m– aya.m vuccati, raahula,
ajjhattikaa tejodhaatu. Yaa ceva kho pana ajjhattikaa tejodhaatu
yaa ca baahiraa tejodhaatu tejodhaaturevesaa. Ta.m ‘neta.m mama,
nesohamasmi, na meso attaa’ti– evameta.m yathaabhuuta.m
sammappa~n~naaya da.t.thabba.m. Evameta.m yathaabhuuta.m
sammappa~n~naaya disvaa tejodhaatuyaa nibbindati, tejodhaatuyaa citta.m
viraajeti.

“Tejosama.m, raahula, bhaavana.m bhaavehi. Tejosama~nhi
te, raahula, bhaavana.m bhaavayato uppannaa manaapaamanaapaa
phassaa citta.m na pariyaadaaya .thassanti. Seyyathaapi, raahula,
tejo sucimpi dahati, asucimpi dahati, guuthagatampi dahati,
muttagatampi dahati, khe.lagatampi dahati, pubbagatampi dahati,
lohitagatampi dahati, na ca tena tejo a.t.tiiyati vaa haraayati
vaa jigucchati vaa; evameva kho tva.m, raahula, tejosama.m
bhaavana.m bhaavehi. Tejosama~nhi te, raahula, bhaavana.m bhaavayato
uppannaa manaapaamanaapaa phassaa citta.m na pariyaadaaya .thassanti.

In Sangiti sutta you can find 'tejokasi.na':

346. Dasa kasi.naayatanaani. Pathaviikasi.nameko sa~njaanaati,
uddha.m adho tiriya.m advaya.m appamaa.na.m. Aapokasi.nameko
sa~njaanaati …pe… tejokasi.nameko sa~njaanaati… vaayokasi.nameko
sa~njaanaati… niilakasi.nameko sa~njaanaati… piitakasi.nameko
sa~njaanaati… lohitakasi.nameko sa~njaanaati… odaatakasi.nameko
sa~njaanaati… aakaasakasi.nameko sa~njaanaati…
vi~n~naa.nakasi.nameko sa~njaanaati, uddha.m adho tiriya.m advaya.m
appamaa.na.m.

In Vimuttimagga and Visuddhimagga you can easily find sections with
description of fire kasina practice.

Dmytro