The Adornment of the Spiritual Marriage, by Jan van Ruysbroeck, , at sacred-texts.com
And now I will warn you against another thing which may cause great harm. Sometimes in that hot season there falls the honey-dew of a certain false sweetness, which pollutes the fruit, or utterly spoils it. And it is most apt to fall at noon, in bright sunshine, and in big drops; and it is hardly to be distinguished from rain. So likewise, some men may be robbed of their outward senses by a certain light produced by the devil. And in this light they are enwrapped and ensnared, and at the same time many kinds of images, both false and true, are shown to them, and they are spoken to in diverse ways; and all this is seen and received of them with great delight. And here there fall sometimes the honey-drops of a false sweetness, in which a man may find his pleasure. He who esteems it much receives much of it: and thereby the man is easily polluted, for if he will hold for true those things which are not like to truth, for the reason that they have been shown or spoken to him, he falls into error and the fruit of virtue is lost. But those who have trodden the ways whereof I have written before, though they may be tempted by this spirit and this light, they will recognise them and will not be harmed.