Author Paul Tremblay recently posted Lovecraft’s notes for his novella At the Mountains of Madness on Instagram. A bit of Google searching led me to this article at Slate from 2013, which you can read for more details.
Below is a large version of HPL’s notes. Enjoy!
(And be sure to check out Paul Tremblay’s book A Head Full of Ghosts, “a chilling thriller that brilliantly blends domestic drama, psychological suspense, and a touch of modern horror, reminiscent of Mark Z. Danielewski’s House of Leaves.”)