Issue installing elasticsearch 1.0.6

$ echo "deb http://packages.elasticsearch.org/elasticsearch/1.0/debian stable main" | sudo tee -a /etc/apt/sources.list.d/elasticsearch-1.x.list
deb http://packages.elasticsearch.org/elasticsearch/1.0/debian stable main

$ sudo apt-get update && sudo apt-get install elasticsearch
W: Failed to fetch http://packages.elastic.co/elasticsearch/1.0.6/debian/dists/stable/main/binary-amd64/Packages 404 Not Found [IP: 23.21.78.197 80]

Looks like you are using the wrong repository URL. Here's the official doc for where deb packages are hosted:

Maybe the following thread helps you as well: