Leonardo da Vinci seemed to have been a big fan of horses, and even his rough sketches possess an almost magical lifelike quality, both in their detail and in their perspective. read more
When you realise that what you will now be drawing is very different from the idealised thing you planned on drawing, you will draw the horse as it actually is, rather than what you think is there. This is tough to do, but can be developed with practice. read more
Notice that it would be very hard and time-consuming to create a perfect, complete reference sheet—for example, you'd need to learn the bones, tendons, muscles, and veins of the horse to draw it realistically from imagination. read more