 We say that a polygon $P$ is inscribed in another polygon $Q$ when all the vertices of $P$ belong to the perimeter of $Q$. We also say in this case that $Q$ is circumscribed to $P$. Given a triangle $T$, let $\ell$ be the largest side of a square inscribed in $T$  and $L$ is the shortest side of a square circumscribed to $T$ . Find the smallest possible value of the ratio $L/\ell$ .
1. **Define the problem and variables:**
   - Given a triangle \( \triangle ABC \) with vertices \( A(0, a) \), \( B(-b, 0) \), and \( C(c, 0) \).
   - We need to find the smallest possible value of the ratio \( \frac{L}{\ell} \), where \( \ell \) is the largest side of a square inscribed in \( \triangle ABC \) and \( L \) is the shortest side of a square circumscribed around \( \triangle ABC \).

2. **Find the largest side of the inscribed square:**
   - Consider a square \( DEFG \) inscribed in \( \triangle ABC \) with vertices \( D(-\lambda, 0) \), \( E(-\lambda, \frac{a(b-\lambda)}{b}) \), \( F(\frac{c \lambda}{b}, \frac{a(b-\lambda)}{b}) \), and \( G(\frac{c \lambda}{b}, 0) \).
   - For \( DEFG \) to be a square, the side length must be equal. This condition is satisfied when \( \lambda = \frac{ab}{a+b+c} \).
   - The side length of the inscribed square is then \( \ell = \frac{a(b+c)}{a+b+c} \).

3. **Find the shortest side of the circumscribed square:**
   - Consider a line through \( C \) with slope \( m \): \( y = m(x - c) \).
   - The line through \( B \) perpendicular to \( CH \) is \( y = -\frac{1}{m}(x + b) \). This line intersects \( CH \) at point \( H \left( \frac{cm^2 - b}{m^2 + 1}, -\frac{m(b+c)}{m^2 + 1} \right) \).
   - The line through \( A \) perpendicular to \( HI \) is \( y - a = mx \). This line intersects \( HI \) at point \( I \left( -\frac{am + b}{m^2 + 1}, \frac{a + bm}{m^2 + 1} \right) \).
   - The line through \( C \) perpendicular to \( IJ \) is \( y = -\frac{1}{m}(x - c) \). This line intersects \( IJ \) at point \( J \left( \frac{c - am}{m^2 + 1}, \frac{a + cm}{m^2 + 1} \right) \).
   - For \( CHIJ \) to be a square, the side length must be equal. This condition is satisfied when \( m = \frac{b+c-a}{c} \).
   - The side length of the circumscribed square is then \( L = \frac{(b+c)c}{\sqrt{(b+c-a)^2 + c^2}} \).

4. **Calculate the ratio \( \frac{L}{\ell} \):**
   - Substitute the expressions for \( L \) and \( \ell \):
     \[
     \frac{L}{\ell} = \frac{\frac{(b+c)c}{\sqrt{(b+c-a)^2 + c^2}}}{\frac{a(b+c)}{a+b+c}}
     \]
   - Simplify the ratio:
     \[
     \frac{L}{\ell} = \frac{(b+c)c (a+b+c)}{a(b+c) \sqrt{(b+c-a)^2 + c^2}}
     \]
     \[
     \frac{L}{\ell} = \frac{c (a+b+c)}{a \sqrt{(b+c-a)^2 + c^2}}
     \]

5. **Find the minimum value of the ratio:**
   - To find the minimum value, we need to analyze the expression \( \frac{c (a+b+c)}{a \sqrt{(b+c-a)^2 + c^2}} \).
   - This expression is minimized when the denominator is maximized, which occurs when \( (b+c-a)^2 + c^2 \) is maximized.
   - By symmetry and geometric considerations, the minimum value of the ratio \( \frac{L}{\ell} \) is achieved when the triangle is equilateral.

6. **Conclusion:**
   - For an equilateral triangle, the ratio \( \frac{L}{\ell} \) simplifies to a constant value.

The final answer is \( \boxed{2} \).