As we can read up on the Wikipedia, the Brocken spectre "is the apparently enormous and magnified shadow of an observer, cast upon the upper surfaces of clouds opposite the sun".
Due to the frequent local optimal conditions for this phenomena to take place, the peak of Brocken - Harz Mountains, Germany - gave its name to this particular atmospheric halo. However, its presence is frequent in mountain regions, as long as you are walking above the clouds and the sun is on the right angle to project your shadow onto them.
Strangely, these conditions in Madeira are not the easiest to find. Most of the times the atmosphere is either fully clouded or not at all.
Or, as one fellow hiker wisely pointed, on the vast majority of Madeira hikes you're walking in the cloud.
Sometimes, nevertheless, generally at morning or evening times, we can also have a glimpse of this optical phenomenon, while hiking along our highest peaks:
The Spectre of Brocken, photographed two days ago, at evening time, on the trail and close to Pico do Areeiro.Picture taken with Nikon D40X and cheap AF-S Nikkor 18-55mm f/3.5-5.6 G II ED with B+W 52 E KR3 1.2* filter.
Legendary among mountaineers, the Spectre of Brocken has a mixed fame, which is both mystical and sinister. Perhaps the most famous of the latter connotation was achieved on the nineteen century, during the first successful climb of the Matterhorn.
The mountain, "conquered" in 1865, by a party of seven, claimed the lives of four on the descent, falling to their deaths due to a broken rope.
According to Edward Whymper, the expedition leader, on his book "The Ascent Of The Matterhorn", this tragic finale was preceded by a spectral vision forming in the clouds nearby and resembling crosses.
To this day many Historians still claim that the phenomena they saw was simply the Brocken spectre playing games with their already exhausted minds.
The spectral phenomena witnessed by Edward Whimper and his companions, while descending from the first ascent of the Matterhorn, as illustrated on his book "The Ascent Of The Matterhorn".