CC Madhya 13.67

bhakta-gaṇa anubhave, nāhi jāne āna
śrī-bhāgavata-śāstra tāhāte pramāṇa
Word for word: 
bhakta-gaṇa — all devotees; anubhave — could perceive; nāhi jāne — do not know; āna — others; śrī-bhāgavata-śāstra — the revealed scripture Śrīmad-Bhāgavatam; tāhāte — in that connection; pramāṇa — evidence.
Translation: 
Śrī Caitanya Mahāprabhu’s dancing before the Ratha-yātrā car could be perceived only by pure devotees. Others could not understand. Descriptions of Lord Kṛṣṇa’s uncommon dancing can be found in the revealed scripture Śrīmad-Bhāgavatam.
Purport: 

Lord Śrī Kṛṣṇa expanded Himself into many forms while engaged in the rāsa-līlā dance, and He also expanded Himself when He married 16,000 wives in Dvārakā. The same process was adopted by Śrī Caitanya Mahāprabhu when He expanded Himself into seven forms to dance in each and every group of the saṅkīrtana party. These expansions were appreciated by pure devotees, including King Pratāparudra. Although for reasons of external formality Śrī Caitanya Mahāprabhu refused to see King Pratāparudra because he was a king, King Pratāparudra became one of the Lord’s most confidential devotees by the Lord’s special mercy upon him. The King could see Śrī Caitanya Mahāprabhu simultaneously present in all seven groups. As confirmed in Śrīmad-Bhāgavatam, one cannot see the expansions of the transcendental forms of the Lord unless one is a pure devotee of the Lord.