Ramayana
ईदृशो ह्यश्वमेधस्य प्रभावः पुरुषर्षभौ । स्त्रीभूतः पौरुषं लेभे यच्चान्यदपि दुर्लभम् ॥ 7-90-24 ॥
Such, O you two bulls among men, is the power of the horse-sacrifice, by which one who had become a woman regained his manhood, and gained also other things hard to obtain.
english translation