Guru Nanak Dev

(born in 1496 AD) has made references to Kundalini awakening as mentioned below:

“A pure heart is the golden vessel to fill the Divine Nectar which is to be sucked from the ‘Dasham Dwar’ through the two channels ‘Ida’ and ‘Pingala’.” Dasham Dwar means Brahmarandhra. (Sahasrara Chakra).

‘God has made this human body a house with six Chakras and has established the light of spirit in it. Cross the ocean of Maya and meet the eternal God who does not come, who does not go, who neither takes birth nor dies. When your six Chakras meet in line, Surati (Kundalini) takes you beyond distortions.’ (Sri Guru Granth). Note that the seventh Chakra was not open at this time.