Euripides alludes to this in his Ion; where he makes latona recline herself against a Palm tree, when she is going to produce Apollo and Diana.
"A New System; or, an Analysis of Antient Mythology. Volume II. (of VI.)"
Jacob Bryant
latona, mother of Apollo and Diana, was magnificently certain that in all time, nor in eternity to come, could there be a son and daughter so perfect in beauty, in wisdom, and in power as the two that were her own.
"A Book of Myths"
Jean Lang
And to her boastful words latona gave ear, and anger began to grow in her heart.
"A Book of Myths"
Jean Lang