Vaishnava Samhita. Shri Vallabhacharya Charitam I. Vol III Book VII Chp 2 Shloka 17

श्रीसद्गुरुरुवाच 
इत्युक्तः पाण्डुरङ्गेन वल्लभो विस्मयङ्गतः  |
स्मरन् स्वप्नगतं विष्णुं चन्द्रभागातटे स्थितः  ||

Shri Sadguru said

Instructed so by Shri Panduranga, Shri Vallabha was surprised. He was waiting on the bank of the Yamuna, meditating upon Shri Vishnu, who gave darshan in his dream.