what is the meaning of a day dream by samuel taylor coolridge

The poem describes a vision the narrator has of a previous time in his life. He remembers a time when Mary (named in the poem) and one other person spent time together. One might assume this was addressed to William Wordsworth and his sister Dorothy with whom Coleridge spent much time. For a time they were nearly inseperable.

i am working an assistant professor so i need some detail to teach the students, thank you.