Hora Sara
बालवृद्धातुरावन्ध्या मुक्त्वा चान्यासु लक्षणम्। त्रयोदशनिशाः स्नानादृतुकालं प्रचक्षते॥२॥
Barring children, old, sickly and barren women, the Ritu Kala (period of conception) in the case of other women is declared to be 13 nights after bathing (on the 4th day).
english translation
bAlavRddhAturAvandhyA muktvA cAnyAsu lakSaNam। trayodazanizAH snAnAdRtukAlaM pracakSate॥2॥
hk transliteration by Sanscript