My current novel takes place in a quasi-medival world in which individuals travel by horse. In some early writings, I had some people knowledgeable about horses take me to task about what I was asking the horses to do in a day. I then did some significant internet-based research on hardy horse breeds and found information about the Icelandic horse .
They are the decendents of the Vikings' horses and are rugged little creatures that can carry enormous weight in comparison with their larger cousins.
I have modeled the horses in my novel after these Icelandic horses. Today a horse-owner friend has arranged for me to be able to ride one of these horses.
The culmination of a half-year's research. :)