SB 9.9.25

rākṣasaṁ bhāvam āpannaḥ
 pāde kalmāṣatāṁ gataḥ
vyavāya-kāle dadṛśe
 vanauko-dampatī dvijau
Word for word: 
rākṣasam — man-eating; bhāvam — propensity; āpannaḥ — having gotten; pāde — on the leg; kalmāṣatām — a black spot; gataḥ — obtained; vyavāya-kāle — at the time of sexual intercourse; dadṛśe — he saw; vana-okaḥ — living in the forest; dam-patī — a husband and wife; dvijau — who were brāhmaṇas.
Translation: 
Saudāsa thus acquired the propensity of a man-eater and received on his leg a black spot, for which he was known as Kalmāṣapāda. Once King Kalmāṣapāda saw a brāhmaṇa couple engaged in sexual intercourse in the forest.