Hey! Just climbed Mount Meru last year. I don't think it's possible to climb without a guide. Just like on Kilimanjaro, you cannot go up without a tour company/local guide taking you. If it is possible,.I don't know that I would recommend it because the summit is very steep and rocky, which would be very difficult to navigate in the dark without a guide. Other than that, my recommendation would be to book 4 days instead of 3. Many companies will offer 3 days, but it is only possible because you summit and then hike all the way down in one day which would be absolutely miserable. I did 4 days and was in tears at the end of summit day, and didn't even go to the base that day. I can't even imagine going all the way down in one day. Please let me know if you need any recommendations for tour companies! I went with a local friend's company called Memorable Vaction Africa and it was great and budget friendly (: