Yantra GogglesI doubt you will find yantra goggles on the internet as far as I know they are the product of my own creativity! I have made a couple of prototype models. It is quite easy to make. All that is required for a rough model are 2 cardboad tubes of suitable length + some flat card to make the "mask" part of the goggles along with some tape to attach the tubes. Then design some suitable images/phrases and draw them with appropriate colors onto paper to be attached to the far end of the tubes. The external light, ie sunshine or lightbulb illuminates the images through the paper. If each eye is presented with a different image, and if the length of the tubes and angles etc are correct then an interesting optical effect can be seen where the two images seem to merge in and out of each other. Regarding the sound and light goggles which entrain the brain waves to specific frequencies there are a lot on the market for example:
I have 2 types of such goggles and it would be quite easy to use them as the external light for the yantra goggles so that the frequency (ie beta, alpha and theta etc) of light could be controlled for specific physiological effects. For the scientifically minded there are so many variables that could be played around with and experimented with to obtain the optimum beneficial effect + learn the principles involved. All the lore and and ancient information about Yantra Yoga could also be studied to enhance the practice.
I remember when I was much younger seeing someone meditating on tv. For the specific practice that they were doing they sat inside a "box" for want of a better term. They sat in lotus posture inside this box facing east as the sun was rising. Exactly positioned on the east face of the box was a hole near the 3rd eye chakra so that only the forhead was struck with the dawn rays of the sun. I think this sensation of the sunlight near the 3rd eye chakra helped him focus his atention there + also some other effects to do with the pituary gland and the life force etc.
Yantra Goggles can be used to help you concentrate on a particular phrase, concept or symbol for extended periods of time. The goggles are cut out all visual distractions. All that you can see, set at a suitable distance of a few inches from your eyes, is your chosen phrase or symbol. The image is back lit either by natural ambient light or integregated LEDs. It is possible that the LED lights can be made to osscilate at desired frequencies to effect the brain waves. Utilising the left/right split of the brain, the goggles may be configured so as to present each hemisphere with appropriate input ie words for the language orientated hemisphere and pictures for the symbol orientated hemisphere. Alternatively the same input may be presented to both eyes simultaneusly.
The idea is not necessarily to constantly gaze at the image. It is suggested that you relax with eyes closed and meditate on your chosen theme. Only periodically should you open your eyes to receive the controlled "input" from the visual sense.