This text describes techniques for setting up optical devices to assist in drawing, particularly the use of mirrors and boxes to reflect and capture perspectives. Instructions include positioning mirrors to capture images from balconies or ceiling representations. Additionally, it covers how to manipulate the angles of mirrors for effective reflection onto a drawing surface.
DRAWING
16. For the parallel picture, you need to close the opening N and open door B; after which the mirror L will be raised to the top of the box, positioning it parallel to the horizon. This setup is useful when on a balcony or high floor to draw a terrace below.
17. If you want to draw a statue located in a somewhat elevated place and represent it as it would be painted on a ceiling, you would need to turn the back of the machine towards the statue and also adjust the box so that door B faces the statue. After opening the door, the mirror L should be placed vertically with the glass facing the statue, and the box should be moved forward or backward, or the mirror raised or lowered until the rays from the statue can be reflected on the glass. When these adjustments of the box or mirror are not sufficient to get this reflection on the glass, you must move the entire machine forward or backward.
IV
Represent objects by making appear on the right what should be on the left.
18. After positioning box X as shown in the figure, you need to open door B and close opening N, then place mirror H in the setup previously described (No. 10.)
19. Raise mirror L towards the top of the box, and incline it towards the first mirror H, such that it forms an angle of 22.5 degrees with the horizon, meaning that
Translation Notes:
The instructions refer to handling a device that seems to resemble a camera obscura or similar optical device used in the practice of drawing during the 18th century. The terms "boîte," "miroir," and "machine" likely relate to components of this device, assisting artists in capturing perspectives and proportions in their drawings.