The sign is at the start of the trail.
Never mind that the trail to the true summit of Mauna Kea is nicely maintained and outlined in rock, the sign requests that you do not take this trail out of respect for the sacredness of the site.
How many people even pause when considering the message on the sign? The trail and the desire to stand atop the real summit of the mountain is substantial. As we pass the trail head and sign each day I usually see several people walking to or standing atop the summit.
Maunakea is historically, culturally, and environmentally significant. Help preserve our cultural and natural landscape and show your respect by not hiking beyond this point to the summit.
I have walked this short trail to the summit several times over the years, though not since the sign appeared. There are no particularly sensitive archaeological sites at the summit. This is in contrast to Lake Waiau, which is ringed with shrines and offerings, is just as sacred, and has no such sign to deter the curious from taking the trail.
Personally I am troubled by this sign. Placing such a sign could very well be counter productive. People are going to ignore it, walking right past it to the summit of Mauna Kea. It simply teaches people to ignore boundaries that could protect sensitive sites.
The summit is public land, belonging to the people of Hawaiʻi. I have trouble with the idea that it should be accessible only to a few on the pretense of religious or cultural heritage. Certainly some might view the summit with less than ideal respect for a special place, simply a pile of rock to be conquered. I suspect most see the summit as more than that, a symbol, a place to sit and think about the world.
I am not a religious person, but still, there are places where I find myself stopping and taking a moment to contemplate our world. The summit is one of these places, a focal point of culture, history, and perhaps the future.
Update Oct 4th: Several folks have commented that a sign educating people about the significance of the place, asking them to be respectful, and asking them to stay within the marked trail would be far more appropriate and productive in terms of protecting the site. I have to agree.
Update Oct 5th: I have posted a follow up article. The response to this article has been impressive, with a lot of heartfelt comments. How we view and respect true summit of Mauna Kea is obviously a subject very important to may people.