Darukkhandhasutta 2.10

2.10

Atthi, āvuso, amumhi dārukkhandhe asubhadhātu, yaṃ nissāya bhikkhu iddhimā cetovasippatto amuṃ dārukkhandhaṃ asubhantveva adhimucceyyā”ti.

Because the element of ugliness exists in the tree trunk. Relying on that a mendicant with psychic powers could determine it to be nothing but ugly.”