Here is the quote from the Apophthegmata Patrum, or the Sayings of the Desert Fathers. It mentions an Abba John, but it does not clarify any further. There were many who lived in Sketis, such as John the Dwarf, John of Thebes, John the Persian, etc., and all of them have teachings recorded in the Sayings.
This quote is from the second volume of The Paradise of the Holy Fathers, published in 1907 by Chatto & Windus:
Abba John used to say, that he saw in a vision one of the old men in a state of stupefaction, and behold, three monks were standing on the shore of a lake, and a voice came to them from heaven (or from the other shore of the lake), which said, "Take ye wings of fire and come to me"; and two of them took wings of fire and flew over to the other side, even as it was told them. Now the third remained behind, and he wept abundantly, and cried out, and at length wings were given to him also, but they were not of fire like those of his companions, for they were weak and feeble wings, and it was only with the greatest difficulty, and after dropping down into the water, and with most painful exertions that he reached the [opposite] shore. And even so is it with this generation, for although it taketh to itself wings, they are not the powerful wings of fire, but it forceth itself to take weak and feeble wings.
It was referred to by Bishop Ignatius (Brianchaninov) in his work, The Arena: An Offering to Contemporary Monasticism, under the chapter, "Troubles are the Special Lot of the Monks of the Last Time". The chapter argues that the intense ascetical labors practiced by the Fathers of the first millennium are not possible for Christians of contemporary times on account of our spiritual weakness and lack of spiritual leadership under genuine Elders (startsy). He argues that the patient enduring of afflictions and temptations are the unique podvig of our times. Patience and humility are more important than extreme attention to fasting and bodily asceticism, which can be harmful to us because of our weakness and our pride. Bishop Ignatius here is in complete agreement with the Optina Elders. Here is how Bishop Ingatius quotes the sayings:
The holy Fahers, the monks of the early times of Christianity, were perfect Christians filled with the Holy Spirit. They had revelations from Above and uttered prophecies about the monasticism of the last days. All these revelations or prophecies agree with one another and declare that the monasticism of the last times will have an extremely feeble life, that it will not be given that abundance of spiritual gifts which the first monks enjoyed, and that the monks of the last times will even find salvation itself only with great difficulty. A certain Egyptian fathers once went into ecstasy and became a witness of a spiritual vision. He saw three monks standing on the sea-shore. From the other shore he heard a voice: 'Receive wings and come to Me.' After the voice, two of the monks received fiery wings and flew across to the other shore. The third one remained where he was. He began to weep and wail. At last wings were given to him too, but not fiery ones--they were so weak that he flew across the sea only with great difficulty and trouble, often becoming so feeble that he sank in the sea. The first two monks represented the monasticism of early times, while the third represented the monasticism of the last times, poor in numbers and in accomplishments.
He goes on to quote further evidence from the Sayings and other sources.
